Chapter 17: Properties of Atoms and the Periodic Tablebkscience.weebly.com/uploads/1/6/3/2/16325492/chap... · 3 The Periodic Table ... composed of tiny particles called atoms

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sections

1 Structure of the Atom

2 Masses of Atoms

3 The Periodic TableLab A Periodic Table of FoodsLab What’s in a name?

Virtual Lab How is thestructure of an atom related to its position on the periodictable?

Atoms Compose All Things—Great and SmallEverything in this photo and the universe iscomposed of tiny particles called atoms.You will learn about atoms and their com-ponents—protons, neutrons, electrons, andquarks.

In your Science Journal, write a fewparagraphs about what you know about atoms. Science Journal

Properties ofAtoms and thePeriodic Table

Walter Bibikow/Index Stock Imagery, NY

Inferring What You Can’t ObserveHow do detectives solve a crime when nowitnesses saw it happen? How do scientistsstudy atoms when they cannot see them? Insituations such as these, techniques must bedeveloped to find clues to answer the ques-tion. Do the lab below to see how cluesmight be gathered.

1. Take an envelope from your teacher.

2. Place an assortment of dried beans in theenvelope and seal it. WARNING: Do noteat any lab materials.

3. Trade envelopes with another group.

4. Without opening the envelope, try to fig-ure out the types and number of beansthat are in the envelope. Record a hypothesis about the contents of theenvelope in your Science Journal.

5. After you record your hypothesis, openthe envelope and see what is inside.

6. Think Critically Describe the contentsof your envelope. Was your hypothesiscorrect?

Start-Up Activities

Preview this chapter’s contentand activities at gpscience.com

Atoms You have probablystudied atoms before. Make thefollowing Foldable to help iden-

tify what you already know, what you want toknow, and what you learned about atoms.

Fold a vertical sheet of paper fromside to side. Make the front edge about1.25 cm shorter thanthe back edge.

Turn lengthwiseand fold into thirds.

Unfold and cut only the top layeralong both folds to make three tabs.

Label each tab as shown.

Identify Questions Before you read the chap-ter, write what you already know about atomsunder the left tab of your Foldable, and writequestions about what you’d like to know underthe center tab. After you read the chapter, listwhat you learned under the right tab.

Know? Learned?Like to know?

STEP 4

STEP 3

STEP 2

STEP 1

505505Walter Bibikow/Index Stock Imagery, NY

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506 CHAPTER 17 Properties of Atoms and the Periodic Table

Scientific Shorthand Do you have a nickname? Do you use abbreviations for long

words or the names of states? Scientists also do this. In fact, sci-entists have developed their own shorthand for dealing withlong, complicated names.

Do the letters C, Al, Ne, and Ag mean anything to you? Eachletter or pair of letters is a chemical symbol, which is a short orabbreviated way to write the name of an element. Chemicalsymbols, such as those in Table 1, consist of one capital letter ora capital letter plus one or two small letters. For some elements,

the symbol is the first letter of the element’sname. For other elements, the symbol is the firstletter of the name plus another letter from itsname. Some symbols are derived from Latin. Forinstance, Argentum is Latin for “silver.” Elementshave been named in a variety of ways. Some ele-ments are named to honor scientists, for places,or for their properties. Other elements arenamed using rules established by an interna-tional committee. Regardless of the origin of thename, scientists derived this international systemfor convenience. It is much easier to write H forhydrogen, O for oxygen, and H

2O for dihydrogen

oxide (water). Because scientists worldwide usethis system, everyone understands what the sym-bols mean.

Structure of the AtomReading Guide

■ Identify the names and symbolsof common elements.

■ Identify quarks as subatomic par-ticles of matter.

■ Describe the electron cloudmodel of the atom.

■ Explain how electrons arearranged in an atom.

Everything that you see, touch, andbreathe is composed of tiny atoms.

Review Vocabularyelement: substance with atoms thatare all alike

New Vocabulary

• atom

• nucleus

• proton

• neutron

• electron

• quark

• electron cloud

Table 1 Symbols of Some Elements

Element Symbol Element Symbol

Aluminum Al Iron Fe

Calcium Ca Mercury Hg

Carbon C Nitrogen N

Chlorine Cl Oxygen O

Gold Au Potassium K

Hydrogen H Sodium Na

SECTION 1 Structure of the Atom 507

Electroncloud

Nucleus

Neutron(No charge)

Quarks

Quarks

Proton(1� charge)Atom

Figure 1 The nucleus of the atomcontains protons and neutrons thatare composed of quarks. The protonhas a positive charge and the neu-tron has no charge. A cloud of nega-tively charged electrons surroundsthe nucleus of the atom.

Atomic Components An element is matter that is composed of one type of atom,

which is the smallest piece of matter that still retains the prop-erty of the element. For example, the element silver is com-posed of only silver atoms and the element hydrogen iscomposed of only hydrogen atoms. Atoms are composed ofparticles called protons, neutrons, and electrons, as shown inFigure 1. Protons and neutrons are found in a small, positively-charged center of the atom called the nucleus that is sur-rounded by a cloud containing electrons. Protons are particleswith an electrical charge of 1�. Neutrons are neutral particlesthat do not have an electrical charge. Electrons are particleswith an electrical charge of 1�. Atoms of different elementsdiffer in the number of protons they contain.

What are the particles that make up the atomand where are they located?

Quarks—Even Smaller ParticlesAre the protons, electrons, and neutrons that make

up atoms the smallest particles that exist? Scientists hypothesizethat electrons are not composed of smaller particles and are one of the most basic types of particles. Protons and neu-trons, however, are made up of smaller particles called quarks.So far, scientists have confirmed the existence of six uniquelydifferent quarks. Scientists theorize that an arrangement ofthree quarks held together with the strong nuclear force pro-duces a proton. Another arrangement of three quarks producesa neutron. The search for the composition of protons and neu-trons is an ongoing effort.

Topic: Particle ResearchVisit gpscience.com for Web linksto information about particleresearch at Fermi NationalAccelerator Laboratory.

Activity Write a paragraphdescribing the information thatyou found at the site.



Figure 2 The Tevatron is ahuge machine. The aerial photo-graph of Fermi NationalAccelerator Laboratory showsthe circular outline of theTevatron particle accelerator.The close-up photograph of theTevatron gives you a better viewof the tunnel. Infer Why is such a long tunnelneeded?

Figure 3 Bubble chambers canbe used by scientists to study thetracks left by subatomic particles.

Finding Quarks To study quarks, scientists acceleratecharged particles to tremendous speeds and then force them tocollide with—or smash into—protons. This collision causes theproton to break apart. The Fermi National AcceleratorLaboratory, a research laboratory in Batavia, Illinois, houses amachine that can generate the forces that are required to collideprotons. This machine, the Tevatron, shown in Figure 2, isapproximately 6.4 km in circumference. Electric and magnetic

fields are used to accelerate, focus and collidethe fast-moving particles.

The particles that result from the collisioncan be detected by various collection devises.Often, scientists use multiple collection devicesto collect the most possible information aboutthe particles created in a collision. Just as policeinvestigators can reconstruct traffic accidentsfrom tire marks and other clues at the scene,scientists are able to examine and gather infor-mation about the particles, as shown inFigure 3. Scientists use inference to identify thesubatomic particles and to reveal informationabout each particle’s inner structure.

The Sixth Quark Finding evidence for theexistence of the quarks was not an easy task.Scientists found five quarks and hypothesizedthat a sixth quark existed. However, it took ateam of nearly 450 scientists from around theworld several years to find the sixth quark.The tracks of the sixth quark were hard todetect because only about one billionth of apercent of the proton collisions performedshowed the presence of a sixth quark—typically referred to as the top quark.

(tl)Science Photo Library/Photo Researchers, (tr)Hank Morgan/Science Source/Photo Researchers, (b)Photo Researchers


Models—Tools for ScientistsScientists and engineers use models to represent things that

are difficult to visualize—or picture in your mind. You mighthave seen models of buildings, the solar system, or airplanes.These are scaled-down models. Scaled-down models allow youto see either something too large to see all at once, or somethingthat has not been built yet. Scaled-up models are often used tovisualize things that are too small to see. To give you an idea ofhow small the atom is, it would take about 24,400 atoms stackedone on top of the other to equal the thickness of a sheet of alu-minum foil. To study the atom, scientists have developed scaled-up models that they can use to visualize how the atom isconstructed. For the model to be useful, it must support all ofthe information that is known about matter and the behavior ofatoms. As more information about the atom is collected, scien-tists change their models to include the new information.

Explain how models can simplify science.

The Changing Atomic Model You know now that all mat-ter is composed of atoms, but this was not always known.Around 400 B.C., Democritus proposed the idea that atomsmake up all substances. However, another famous Greekphilosopher, Aristotle, disputed Democritus’s theory and pro-posed that matter was uniform throughout and was not com-posed of smaller particles. Aristotle’s incorrect theory wasaccepted for about 2,000 years. In the 1800s, John Dalton, anEnglish scientist, was able to offer proof that atoms exist.

Dalton’s model of the atom, a solid sphere shown in Figure 4,was an early model of the atom. As you can see in Figure 5, themodel has changed somewhat over time. Dalton’s moderniza-tion of Aristotle’s idea of the atom provided a physical explana-tion for chemical reactions. Scientists could then express thesereactions in quantitative terms using chemical symbols andequations.

Modeling an Aluminum AtomProcedure1. Arrange thirteen 3-cm

circles cut from orangepaper and fourteen 3-cmcircles cut from blue paperon a flat surface to repre-sent the nucleus of anatom. Each orange circlerepresents one proton, andeach blue circle representsone neutron.

2. Position two holespunched from red paperabout 20 cm from yournucleus.

3. Position eight punchedholes about 40 cm fromyour nucleus.

4. Position three punchedholes about 60 cm fromyour nucleus.

Analysis1. How many protons, neu-

trons, and electrons does an aluminum atom have?

2. Explain how your circlesmodel an aluminum atom.

3. Explain why your modeldoes not accurately represent the true size and distances in an aluminum atom.

Figure 4 John Dalton’s atomicmodel was a simple sphere.

Sheila Terry/Science Photo Library/Photo Researchers

Figure 5


VISUALIZING THE ATOMIC MODEL

The ancient Greek philosopher Democritus proposed that elements consisted of tiny, solid particles that could not besubdivided (A). He called these particles atomos, meaning

“uncuttable.”This concept of the atom’s structure remained largelyunchallenged until the 1900s, when researchers began to discoverthrough experiments that atoms were composed of still smallerparticles. In the early 1900s, a number of models for atomic structure were proposed (B-D).The currently accepted model (E)evolved from these ideas and the work of many other scientists.

THOMSON MODEL, 1904 English physicist JosephJohn Thomson inferred from his experiments thatatoms contained small, negatively charged particles.He thought these “electrons” (in red) were evenlyembedded throughout a positively charged sphere,much like chocolate chips in a ball of cookie dough.

BRUTHERFORD MODEL, 1911 Another British

physicist, Ernest Rutherford, proposed thatalmost all the mass of an atom—and all its posi-tive charges—were concentrated in a centralatomic nucleus surrounded by electrons.

C

BOHR MODEL, 1913 Danish physicist Niels Bohrhypothesized that electrons traveled in fixed orbitsaround the atom’s nucleus. James Chadwick, a student of Rutherford, concluded that the nucleus containedpositive protons and neutral neutrons.

DELECTRON CLOUD MODEL, CURRENT According

to the currently accepted model of atomic struc-ture, electrons do not follow fixed orbits but tendto occur more frequently in certain areas aroundthe nucleus at any given time.

E

DEMOCRITUS’S UNCUTTABLE ATOM

A

Electroncloud

Nucleus

Positivelychargednucleus

“Empty space”containing electrons

Negativelychargedelectron

Ball ofpositivecharge


Self Check1. List the chemical symbols for the elements carbon, alu-

minum, hydrogen, oxygen, and sodium.

2. Identify the names, charges, and locations of threekinds of particles that make up an atom.

3. Identify the smallest particle of matter. How were theydiscovered?

4. Describe the electron cloud model of the atom.

5. Think Critically Explain how a rotating electric fanmight be used to model the atom. Explain how therotating fan is unlike an atom.

6. Use Numbers The mass of a proton is estimated to be1.6726 � 10-24 g and the mass of an electron is esti-mated to be 9.1093 � 10-28 g. How many times largeris the mass of a proton compared to the mass of anelectron?

7. Calculate What is the difference between the mass of a proton and the mass of an electron?

The Electron Cloud Model By 1926,scientists had developed the electron cloudmodel of the atom that is in use today. Anelectron cloud is the area around thenucleus of an atom where its electrons aremost likely found. The electron cloud is100,000 times larger than the diameter ofthe nucleus. In contrast, each electron in the cloud is much smaller than a singleproton.

Because an electron’s mass is small and theelectron is moving so quickly around thenucleus, it is impossible to describe its exactlocation in an atom. Picture the spokes on amoving bicycle wheel. They are moving soquickly that you can’t pinpoint any singlespoke. All you see is a blur that contains all ofthe spokes somewhere within it. In the sameway, an electron cloud is a blur containing all of the electrons ofthe atom somewhere within it. Figure 6 illustrates what the electron cloud might look like.

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Nucleus

Electron cloud

Figure 6 The electrons arelocated in an electron cloud sur-rounding the nucleus of the atom.

SummaryScientific Shorthand

• Scientists use chemical symbols as shorthandwhen naming elements.

Atomic Components

• Atoms are composed of small particles thathave known charges.

• The particles that make up the atom arelocated in predictable locations within theatom.

Quarks—Even Smaller Particles

• So far, scientists have confirmed the existenceof six different quarks.

Models—Tools for Scientists

• Models are used by scientists to simplify thestudy of concepts and things.

• The current atomic model is an accumulationof over two hundred years of knowledge.

• The electron cloud model is the currentatomic model.

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Atomic MassThe nucleus contains most of the mass of the atom because

protons and neutrons are far more massive than electrons. Themass of a proton is about the same as that of a neutron—approximately 1.6726 � 10�24 g, as shown in Table 2. The massof each is approximately 1,836 times greater than the mass of theelectron. The electron’s mass is so small that it is considered neg-ligible when finding the mass of an atom, as shown in Figure 7.

If you were asked to estimate the height of your schoolbuilding, you probably wouldn’t give an answer in kilometers.The number would be too cumbersome to use. Consideringthe scale of the building, you would more likely give the heightin a smaller unit, meters. When thinking about the smallmasses of atoms, scientists found that even grams were notsmall enough to use for measurement. Scientists need a unitthat results in more manageable numbers. The unit of meas-urement used for atomic particles is the atomic mass unit(amu). The mass of a proton or a neutron is almost equal to1 amu. This is not coincidence—the unit was defined that way.The atomic mass unit is defined as one-twelfth the mass of acarbon atom containing six protons and six neutrons.Remember that the mass of the carbon atom is containedalmost entirely in the mass of the protons and neutrons thatare located in the nucleus. Therefore, each of the 12 particlesin the nucleus must have a mass nearly equal to one.

Where is the majority of the mass of anatom located?

Masses of AtomsReading Guide

■ Compute the atomic mass andmass number of an atom.

■ Identify the components of isotopes.

■ Interpret the average atomicmass of an element.

Some elements naturally exist inmore than one form—radioactiveand nonradioactive.

Review Vocabularymass: amount of matter in an object

New Vocabulary

• atomic number

• mass number

• isotope

• average atomic mass

Table 2 SubatomicParticle Masses

Particle Mass (g)

Proton 1.6726 � 10�24

Neutron 1.6749 � 10�24

Electron 9.1093 � 10�28

Figure 7 If you held a textbookand placed a paper clip on it, youwouldn’t notice the added massbecause the mass of a paper clip issmall compared to the mass of thebook. In a similar way, the massesof an atom’s electrons are negligi-ble compared to an atom’s mass.

Matt Meadows

SECTION 2 Masses of Atoms 513

Table 3 Mass Numbers of Some Atoms

Element Symbol Atomic Protons Neutrons Mass Average Number Number Atomic Mass*

Boron B 5 5 6 11 10.81 amu

Carbon C 6 6 6 12 12.01 amu

Oxygen O 8 8 8 16 16.00 amu

Sodium Na 11 11 12 23 22.99 amu

Copper Cu 29 29 34 63 63.55 amu

*The atomic mass units are rounded to two decimal places.

Protons Identify the Element You learned earlier thatatoms of different elements are different because they have dif-ferent numbers of protons. In fact, the number of protons tellsyou what type of atom you have and vice versa. For example,every carbon atom has six protons. Also, all atoms with sixprotons are carbon atoms. Atoms with eight protons are oxy-gen atoms. The number of protons in an atom is equal to anumber called the atomic number. The atomic number of car-bon is six. Therefore, if you are given any one of the follow-ing—the name of the element, the number of protons in theelement, or the atomic number of the element, you can deter-mine the other two.

Which element is an atom with six protons in the nucleus?

Mass Number The mass number of an atom is the sum ofthe number of protons and the number of neutrons in thenucleus of an atom. Look at Table 3 and see if this is true.

If you know the mass number and the atomic number of anatom, you can calculate the number of neutrons. The number ofneutrons is equal to the atomic number subtracted from themass number.

Atoms of the same element with different numbers of neu-trons can have different properties. For example, carbon with amass number equal to 12, or carbon-12, is the most commonform of carbon. Carbon-14 is present on Earth in much smallerquantities. Carbon-14 is radioactive and carbon-12 is not.

number of neutrons � mass number � atomic number


Isotopes Not all the atoms of an element have the same number of

neutrons. Atoms of the same element that have different num-bers of neutrons are called isotopes. Suppose you have a sampleof the element boron. Naturally occurring atoms of boron havemass numbers of 10 or 11. How many neutrons are in a boronatom? It depends upon the isotope of boron to which you arereferring. Obtain the number of protons in boron from the peri-odic table. Then use the formula on the previous page to calcu-late the number of neutrons in each boron isotope. You candetermine that boron can have five or six neutrons.

Uranium-238 has 92 protons. How manyneutrons does it have?

Carbon Dating Livingorganisms on Earth con-tain carbon. Carbon-12makes up 99 percent ofthis carbon. Carbon-13 andcarbon-14 make up theother one percent. Whichisotopes are archaeolo-gists most interested inwhen they determine theage of carbon-containingremains? Explain youranswer in your ScienceJournal.

Radioactive Isotopes Help Tell Time

Atoms can be used to meas-ure the age of bones or rock

formations that are millions ofyears old. The time it takes forhalf of the radioactive atoms ina piece of rock or bone to changeinto another element is calledits half-life. Scientists use thehalf-lives of radioactive isotopesto measure geologic time.

Identifying the ProblemThe table above lists the half-lives of a sample of radioactive isotopes and into

which elements they change. For example, it would take 5,715 years for half of thecarbon-14 atoms in a rock to change into atoms of nitrogen-14. After another5,715 years, half of the remaining carbon-14 atoms will change, and so on. You canuse these radioactive clocks to measure different periods of time.

Solving the Problem1. How many years would it take half of the rubidium-87 atoms in a piece of rock

to change into strontium-87? How many years would it take for 75% of theatoms to change?

2. After a long period, only 25% of the atoms in a rock remained uranium-238.How many years old would you predict the rock to be? The other 75% of theatoms are now which radioactive element?

Half-Lives of Radioactive Isotopes

Radioactive Changes to This Half-Life

Element Element

uranium-238 lead-206 4,460 million years

potassium-40 argon-40, calcium-40 1,260 million years

rubidium-87 strontium-87 48,800 million years

carbon-14 nitrogen-14 5,715 years

SECTION 2 Masses of Atoms 515

Self Check1. Identify the mass number and atomic number of a

chlorine atom that has 17 protons and 18 neutrons.

2. Explain how the isotopes of an element are alike andhow are they different.

3. Explain why the atomic mass of an element is an aver-age mass.

4. Explain how you would calculate the number of neu-trons in potassium-40.

5. Think Critically Chlorine has an average atomic massof 35.45 amu. The two naturally occurring isotopes ofchlorine are chlorine-35 and chlorine-37. Why does thisindicate that most chlorine atoms contain 18 neutrons?

SummaryAtomic Mass

• The nucleus contains most of the mass of anatom.

• The mass of a proton and neutron are approx-imately equal.

• The mass of an electron is considered negligi-ble when finding the mass of an atom.

• The unit of measurement for atomic particlesis the atomic mass unit.

• The carbon-12 isotope was used to define theatomic mass unit.

• The number of protons identifies the element.

Isotopes

• Atoms of the same element with differentnumbers of neutrons are called isotopes.

• The average atomic mass of an element is the weighted-average mass of the mixture of isotopes.

6. Use Numbers If a hydrogen atom has 2 neutrons and1 proton, what is its mass number?

7. Use Tables Use the information in Table 2 to find the mass in kilograms of each subatomic particle.

Identifying Isotopes Models of two isotopesof boron are shown in Figure 8. Because thenumbers of neutrons in the isotopes are differ-ent, the mass numbers are also different. You usethe name of the element followed by the massnumber of the isotope to identify each isotope:boron-10 and boron-11. Because most elementshave more than one isotope, each element has anaverage atomic mass. The average atomic massof an element is the weighted-average mass ofthe mixture of its isotopes. For example, four outof five atoms of boron are boron-11, and one outof five is boron-10. To find the weighted-averageor the average atomic mass of boron, you wouldsolve the following equation:

The average atomic mass of the element boron is 10.8 amu.Note that the average atomic mass of boron is close to the massof its most abundant isotope, boron-11.

�45

�(11 amu) � �15

�(10 amu) � 10.8 amu


�

� ��

�

�

��

� �

Boron-11Boron-10

NucleusNucleus

5 Neutrons

6 Neutrons

5 Protons

5 Protons

5 Electrons

5 Electrons

Figure 8 Boron-10 and boron-11 are two isotopes ofboron. These two isotopes differ by one neutron.Explain why these atoms areisotopes.



Organizing the Elements On a clear evening, you can see one of the various phases of

the Moon. Each month, the Moon seems to grow larger, thensmaller, in a repeating pattern. This type of change is periodic.Periodic means “repeated in a pattern.” The days of the week areperiodic because they repeat themselves every seven days. Thecalendar is a periodic table of days and months.

In the late 1800s, Dmitri Mendeleev,a Russian chemist, searched for a way toorganize the elements. When hearranged all the elements known at thattime in order of increasing atomicmasses, he discovered a pattern. Figure 9shows Mendeleev’s early periodic chart.Chemical properties found in lighterelements could be shown to repeat in heavier elements. Because the patternrepeated, it was considered to be periodic. Today, this arrangement iscalled a periodic table of elements. Inthe periodic table, the elements arearranged by increasing atomic numberand by changes in physical and chemicalproperties.

The Periodic TableReading Guide

■ Explain the composition of theperiodic table.

■ Use the periodic table to obtaininformation.

■ Explain what the terms metal,nonmetal, and metalloid mean.

The periodic table is an organized list of the elements that compose allliving and nonliving things that areknown to exist in the universe.

Review Vocabularychemical property: any characteristicof a substance that indicates whetherit can undergo a certain chemicalchange

New Vocabulary

• periodic table

• group

• electron dot diagram

• period

Figure 9 Mendeleev discoveredthat the elements had a periodicpattern in their chemical proper-ties. Notice the question marks inhis chart. These were elementsthat had not been discoveredat that time.

Science Museum/Science & Society Picture Library

SECTION 3 The Periodic Table 517

Mendeleev’s Predictions Mendeleev had to leave blankspaces in his periodic table to keep the elements properly linedup according to their chemical properties. He looked at theproperties and atomic masses of the elements surrounding theseblank spaces. From this information, he was able to predict theproperties and the mass numbers of new elements that had notyet been discovered. Table 4 shows Mendeleev’s predicted prop-erties for germanium, which he called ekasilicon. His predic-tions proved to be accurate. Scientists later discovered thesemissing elements and found that their properties wereextremely close to what Mendeleev had predicted.

How did Mendeleev organize his periodic chart?

Improving the Periodic Table Although Mendeleev’sarrangement of elements was successful, it did need some changes.On Mendeleev’s table, the atomic mass gradually increased fromleft to right. If you look at the modern periodic table, shown inTable 5, you will see several examples, such as cobalt and nickel,where the mass decreases from left to right. You also might noticethat the atomic number always increases from left to right. In 1913,the work of Henry G.J. Moseley, a young English scientist, led tothe arrangement of elements based on their increasing atomicnumbers instead of an arrangement based on atomic masses. Thisnew arrangement seemed to correct the problems that hadoccurred in the old table. The current periodic table uses Moseley’sarrangement of the elements.

How is the modern periodic table arranged?

Table 4 Mendeleev’s Predictions

Predicted Properties Actual Propertiesof Ekasilicon (Es) of Germanium (Ge)

Existence Predicted—1871 Actual Discovery—1886

Atomic mass � 72 Atomic mass � 72.61

High melting point Melting point � 938°C

Density � 5.5 g/cm3 Density � 5.323 g/cm3

Dark gray metal Gray metal

Density of EsO2 � 4.7 g/cm3 Density of GeO2 � 4.23 g/cm3

Organizing a PersonalPeriodic TableProcedure1. Collect as many of the fol-

lowing items as you canfind: feather, penny, con-tainer of water, pencil,dime, strand of hair, con-tainer of milk, containerof orange juice, square ofcotton cloth, nickel,crayon, quarter, con-tainer of soda, golf ball,sheet of paper, baseball,marble, leaf, paper clip.

2. Organize these items intoseveral columns based ontheir similarities to createyour own periodic table.

Analysis1. Explain the system you

used to group your items.2. Were there any items on

the list that did not fit intoany of your columns?

3. Infer how your activitymodeled Mendeleev’swork in developing theperiodic table of the elements.


PERIODIC TABLE OF THE ELEMENTS

Hydrogen

1

H1.008

Element

Atomic number State ofmatter

Hydrogen

1

H1.008

Lithium

3

Li6.941

Sodium

11

Na22.990

Potassium

19

K39.098

Rubidium

37

Rb85.468

Cesium

55

Cs132.905

Francium

87

Fr(223)

Radium

88

Ra(226)

Actinium

89

Ac(227)

Rutherfordium

104

Rf(261)

Barium

56

Ba137.327

Lanthanum

57

La138.906

Hafnium

72

Hf178.49

Tantalum

73

Ta180.948

Dubnium

105

Db(262)

Seaborgium

106

Sg(266)

Hassium

108

Hs(277)

Meitnerium

109

Mt(268)

Bohrium

107

Bh(264)

Tungsten

74

W183.84

Rhenium

75

Re186.207

Osmium

76

Os190.23

Iridium

77

Ir192.217

Strontium

38

Sr87.62

Yttrium

39

Y88.906

Zirconium

40

Zr91.224

Niobium

41

Nb92.906

Molybdenum

42

Mo95.94

Calcium

20

Ca40.078

Scandium

21

Sc44.956

Titanium

22

Ti47.867

Vanadium

23

V50.942

Chromium

24

Cr51.996

Technetium

43

Tc(98)

Ruthenium

44

Ru101.07

Manganese

25

Mn54.938

Iron

26

Fe55.845

Cobalt

27

Co58.933

Rhodium

45

Rh102.906

Magnesium

12

Mg24.305

Beryllium

4

Be9.012

1

1 2

2

3

4

5

6

7

93 4 5 6 7

Gas

Liquid

Solid

Synthetic

8

The number in parentheses is the mass number of the longest-lived isotope for that element.

The first three symbols tell you the state of matter of the element at room temperature. The fourth symbol identifies elements that are not present in significant amounts on Earth. Useful amounts are made synthetically.

The arrow shows where these elements would fit into the periodic table. They are moved to the bottom of the table to save space.

Rows of elements are called periods. Atomic number increases across a period.

Columns of elements are called groups. Elements in the same group have similar chemical properties.

Cerium

58

Ce140.116

Thorium

90

Th232.038

Uranium

92

U238.029

Neptunium

93

Np(237)

Plutonium

94

Pu(244)

Neodymium

60

Nd144.24

Promethium

61

Pm(145)

Samarium

62

Sm150.36

59

Pr140.908

Protactinium

91

Pa231.036

Lanthanideseries

Actinideseries

Symbol

Atomic mass

Praseodymium


Metal

Metalloid

NonmetalHelium

2

He4.003

Darmstadtium

110

Ds(281)

Unununium

111

Uuu(272)

Ununbium

112

Uub(285)

Ununquadium

114

Uuq(289)

Platinum

78

Pt195.078

Gold

79

Au196.967

Mercury

80

Hg200.59

Thallium

81

Tl204.383

Lead

82

Pb207.2

Bismuth

83

Bi208.980

Astatine

85

At(210)

Radon

86

Rn(222)

Nickel

28

Ni58.693

Copper

29

Cu63.546

Zinc

30

Zn65.409

Gallium

31

Ga69.723

Germanium

32

Ge72.64

Arsenic

33

As74.922

Selenium

34

Se78.96

Bromine

35

Br79.904

Krypton

36

Kr83.798

Palladium

46

Pd106.42

Silver

47

Ag107.868

Cadmium

48

Cd112.411

Indium

49

In114.818

Tin

50

Sn118.710

Antimony

51

Sb121.760

Tellurium

52

Te127.60

Iodine

53

I126.904

Xenon

54

Xe131.293

Aluminum

13

Al26.982

Silicon

14

Si28.086

Phosphorus

15

P30.974

Sulfur

16

S32.065

Chlorine

17

Cl35.453

Argon

18

Ar39.948

Boron

5

B10.811

Carbon

6

C12.011

Nitrogen

7

N14.007

Oxygen

8

O15.999

Fluorine

9

F18.998

Neon

10

Ne20.180

10 11 12

13 14 15 16 17

18

Polonium

84

Po(209)

The names and symbols for elements 111–114 are temporary. Final names will be selected when the elements’ discoveries are verified.

** *

The color of an element’s block tells you if the element is a metal, nonmetal, or metalloid.

* Elements 116 and 118 were thought to have been created. The claim was retracted because the experimental results could not be repeated.**

116

118

* ** *

Europium

63

Eu151.964

Americium

95

Am (243)

Berkelium

97

Bk(247)

Californium

98

Cf(251)

Einsteinium

99

Es(252)

Fermium

100

Fm(257)

Nobelium

102

No(259)

Lawrencium

103

Lr(262)

Mendelevium

101

Md(258)

Holmium

67

Ho164.930

Dysprosium

66

Dy162.500

Terbium

65

Tb158.925

Curium

96

Cm(247)

Gadolinium

64

Gd157.25

Erbium

68

Er167.259

Thulium

69

Tm168.934

Ytterbium

70

Yb173.04

Lutetium

71

Lu174.967

Topic: Periodic TableUpdates Visit gpscience.com for updates tothe periodic table.



The Atom and the Periodic TableObjects often are sorted or grouped according to the prop-

erties they have in common. This also is done in the periodictable. The vertical columns in the periodic table are calledgroups, or families, and are numbered 1 through 18. Elementsin each group have similar properties. For example, in Group 11,copper, silver, and gold have similar properties. Each is a shinymetal and a good conductor of electricity and heat. What isresponsible for the similar properties? To answer this question,look at the structure of the atom.

Electron Cloud Structure You have learned about thenumber and location of protons and neutrons in an atom. Butwhere are the electrons located? How many are there? In a neu-tral atom, the number of electrons is equal to the number ofprotons. Therefore, a carbon atom, with an atomic number ofsix, has six protons and six electrons. These electrons are locatedin the electron cloud surrounding the nucleus.

Scientists have found that electrons within the electroncloud have different amounts of energy. Scientists model theenergy differences of the electrons by placing the electrons inenergy levels, as in Figure 10. Energy levels nearer the nucleushave lower energy than those levels that are farther away.Electrons fill these energy levels from the inner levels (closer tothe nucleus) to the outer levels (farther from the nucleus).

Elements that are in the same group have the same numberof electrons in their outer energy level. It is the number of elec-trons in the outer energy level that determines the chemicalproperties of the element. It is important to understand the linkbetween the location on the periodic table, chemical properties,and the structure of the atom.

Energy

Floor (nucleus)

2 electronsStep 1 = energy level 1



Step 4 = energy level 4 32 electrons

Figure 10 Energy levels inatoms can be represented by a flightof stairs. Each stair step away fromthe nucleus represents an increasein the amount of energy within theelectrons. The higher energy levelscontain more electrons.

Research Physicist Thestudy of nuclear interac-tions is shared by chemistsand physicists. Researchphysicists use their knowl-edge of the physical lawsof nature to explain thebehavior of the atom andits composition. Explain inyour Science Journal whyphysicists would study theamount of energy that elec-trons contain.


Energy Levels These energy levels are named using numbersone to seven. The maximum number of electrons that can becontained in each of the first four levels is shown in Figure 10.For example, energy level one can contain a maximum of twoelectrons. Energy level two can contain a maximum of eightelectrons. Notice that energy levels three and four contain sev-eral electrons. A complete and stable outer energy level will con-tain eight electrons. In elements in periods three and higher,additional electrons can be added to inner energy levelsalthough the outer energy level contains only eight electrons.

Rows on the Table Remember that the atomic numberfound on the periodic table is equal to the number of electronsin an atom. Look at Figure 11. The first row has hydrogen withone electron and helium with two electrons both in energy levelone. Because energy level one is the outermost level containingan electron, hydrogen has one outer electron. Helium has twoouter electrons. Recall from Figure 10 that energy level one canhold only two electrons. Therefore, helium has a full or com-plete outer energy level.

The second row begins with lithium, which has three elec-trons—two in energy level one and one in energy level two.Lithium has one outer electron. Lithium is followed by beryl-lium with two outer electrons, boron with three, and so on untilyou reach neon with eight outer electrons. Again, looking atFigure 10, energy level two can only hold eight electrons.Therefore, neon has a complete outer energy level. Do younotice how the row in the periodic table ends when an outerenergy level is filled? In the third row of elements, the electronsbegin filling energy level three. The row ends with argon, whichhas a full outer energy level of eight electrons.

How many electrons are needed to fill the outerenergy level of sulfur?

Boron5B

Carbon6C

Nitrogen7N

Oxygen8O

Fluorine9F

Helium2

He

Neon10Ne

Hydrogen1H

Lithium3Li

Beryllium4

Be

Aluminum13Al

Silicon14Si

Phosphorus15P

Sulfur16S

Chlorine17Cl

Argon18Ar

Sodium11Na

Magnesium12Mg

Figure 11 One proton and oneelectron are added to each ele-ment as you go across a period inthe periodic table.Explain what the elements in thelast column share in relation to theirouter energy levels.

Topic: Atomic Energy LevelStructure Visit gpscience.com for Web linksto information about the structureof atomic energy levels.

Activity Draw a diagram thatdetails how the energy levels arestructured.



Electron Dot Diagrams Did you notice that hydrogen,lithium, and sodium have one electron in their outer energylevel? Elements that are in the same group have the same num-ber of electrons in their outer energy level. These outer electronsare so important in determining the chemical properties of anelement that a special way to represent them has been devel-oped. American chemist G. N. Lewis created this method whileteaching a college chemistry class. An electron dot diagram usesthe symbol of the element and dots to represent the electrons inthe outer energy level. Figure 12 shows the electron dot diagramfor Group 1 elements. Electron dot diagrams are used also toshow how the electrons in the outer energy level are bondedwhen elements combine to form compounds.

Same Group—Similar Properties The elements in Group17, the halogens, have electron dot diagrams similar to chlorine,shown in Figure 13. All halogens have seven electrons in theirouter energy levels. Since all of the members of a group on theperiodic table have the same number of electrons in their outerenergy level, group members will undergo chemical reactions insimilar ways.

A common property of the halogens is the ability to formcompounds readily with elements in Group 1. Group 1 elementshave only one electron in their outer energy level.Figure 13 shows an example of a compound formed by one suchreaction. The Group 1 element, sodium, reacts easily with theGroup 17 element, chlorine. The result is the compound sodiumchloride, or NaCl—ordinary table salt.

Not all elements will combine readily with other elements.The elements in Group 18 have complete outer energy levels.This special configuration makes Group 18 elements relativelyunreactive. You will learn more about why and how bonds formbetween elements in the later chapters.

Why do elements in a group undergo similarchemical reactions?

H

Li

Na

K

Rb

Cs

Fr

Cl Cl �

Na �

Ne

Figure 12 The elements inGroup 1 have one electron in theirouter energy level. This electrondot diagram represents that oneelectron.

Sodium combines with chlorine togive each element a complete outerenergy level in the resulting com-pound.

The electron dot diagram for Group 17 consists of three sets of paired dots and one single dot.

Neon, a member of Group 18, has afull outer energy level. Neon haseight electrons in its outer energylevel, making it unreactive.

Figure 13 Electron dot dia-grams show the electrons in anelement’s outer energy level.


Regions on the Periodic Table The periodic table has several regions with specific names.

The horizontal rows of elements on the periodic table are calledperiods. The elements increase by one proton and one electronas you go from left to right in a period.

All of the elements in the blue squares in Figure 14 are met-als. Iron, zinc, and copper are examples of metals. Most metalsexist as solids at room temperature. They are shiny, can bedrawn into wires, can be pounded into sheets, and are good con-ductors of heat and electricity.

Those elements on the right side of the periodic table, in yel-low, are classified as nonmetals. Oxygen, bromine, and carbonare examples of nonmetals. Most nonmetals are gases, are brit-tle, and are poor conductors of heat and electricity at room tem-perature. The elements in green are metalloids or semimetals.They have some properties of both metals and nonmetals.Boron and silicon are examples of metalloids.

What are the properties of the elements locatedon the left side of the periodic table?

A Growing Family Scientists around the world are continu-ing their research into the synthesis of elements. In 1994, scien-tists at the Heavy-Ion Research Laboratory in Darmstadt,Germany, discovered element 111. As of 1998, only one isotopeof element 111 has been found. This isotope had a life span of0.002 s. In 1996, element 112 was discovered at the same labora-tory. As of 1998, only one isotope of element 112 has beenfound. The life span of this isotope was 0.00048 s. Both of theseelements are produced in the laboratory by joining smalleratoms into a single atom. The search for elements with higheratomic numbers continues.Scientists think they have syn-thesized elements 114 and 116.However, the discovery ofthese elements has not yetbeen confirmed.

Figure 14 Metalloids are locatedalong the green stair-step line.Metals are located to the left of themetalloids. Nonmetals are locatedto the right of the metalloids.

Metals

Nonmetals

Metalloids

Topic: New Elements Visit gpscience.com for Web linksto information about newlysynthesized elements.

Activity Write a paragraphexplaining how several new ele-ments were synthesized and whosynthesized them.


Self Check1. Identify Use the periodic table to find the name,

atomic number, and average atomic mass of thefollowing elements: N, Ca, Kr, and W.

2. List the period and group in which each of theseelements is found: nitrogen, sodium, iodine, andmercury.

3. Classify each of these elements as a metal, a nonmetal,or a metalloid and give the full name of each: K, Si, Ba,and S.

4. Think Critically The Mendeleev and Mosely periodiccharts have gaps for the as-then-undiscovered elements.Why do you think the chart used by Mosely was moreaccurate at predicting where new elements would beplaced?

SummaryOrganizing the Elements

• Mendeleev organized the elements usingincreasing atomic mass and chemical andphysical properties.

• Mendeleev left blank spaces in his table toallow for elements that were yet undiscovered.

• Moseley corrected the problems in the periodictable by arranging the elements in order ofincreasing atomic number.

The Atom and the Periodic Table

• The vertical columns in the periodic table areknown as groups or families. Elements in agroup have similar properties.

• Electrons within the electron cloud have dif-ferent amounts of energy.

Regions of the Periodic Table

• The periodic table is divided into these regions:periods, metals, nonmetals, and metalloids.

• Scientists around the world are continuing totry to synthesize new elements.

5. Make a Graph Construct a circle graph showingthe percentage of elements classified as metals,metalloids, and nonmetals. Use markers or coloredpencils to distinguish clearly between each sectionon the graph. Record your calculations in your Science Journal.

Elements in the UniverseUsing the technology that is availabletoday, scientists are finding the same ele-

ments throughout the universe. They have been able to studyonly a small portion of the universe, though, because it is sovast. Many scientists believe that hydrogen and helium are thebuilding blocks of other elements. Atoms join together withinstars to produce elements with atomic numbers greater than 1or 2—the atomic numbers of hydrogen and helium. Explodingstars, or supernovas, shown in Figure 15, give scientists evidenceto support this theory. When stars go supernova a mixture ofelements, including the heavy elements such as iron, are flunginto the galaxy. Many scientists believe that supernovas havespread the elements that are found throughout the universe.Promethium, technetium, and elements with an atomic numberabove 92 are rare or are not found on Earth. Some of these ele-ments are found only in trace amounts in Earth’s crust as aresult of uranium decay. Others have been found only in stars.


Figure 15 Scientists think thatsome elements are found in natureonly within stars.

524 CHAPTER 17CORBIS


Real-World QuestionMendeleev’s task of organizing a collection ofloosely related items probably seemed daunt-ing at first. How will using your favorite foodsto create your own periodic table be similar tothe task that Mendeleev had?

Goals■ Organize 20 of your favorite foods into a

periodic table of foods.■ Analyze and evaluate your periodic table

for similar characteristics among groups orfamily members on your table.

■ Infer where new foods added to your tablewould be placed.

Materials11 � 17 paper12- or 18-inch rulercolored pencils or markers

Procedure1. List 20 of your favorite foods and drinks.

2. Describe basic characteristics of each ofyour food and drink items. For example, youmight describe the primary ingredient,nutritional value, taste, and color of eachitem. You also could identify the food groupof each item such as fruits/vegetables,grains, dairy products, meat, and sweets.

3. Create a data table to organize the infor-mation that you collect.

4. Using your data table, construct a periodictable of foods on your 11 � 17 sheet of paper.Determine which characteristics you will use togroup your items. Create families (columns) offood and drink items that share similar charac-teristics on your table.

For example, potato chips, pretzels, andcheese-flavored crackers could be combinedinto a family of salty tasting foods. Create asmany groups as you need, and you do notneed to have the same number of items inevery family.

Conclude and Apply1. Evaluate the characteristics you used to

make the groups on your periodic table. Dothe characteristics of each group adequatelydescribe all the family members? Do thecharacteristics of each group distinguish itsfamily members from the family membersof the other groups?

2. Analyze the reasons why some items didnot fit easily into a group.

3. Infer why chemists have not created a peri-odic table of compounds.

A Periodic Table of F^^ds

Construct a bulletin board of the periodictables of foods created by the class. Howare the tables similar?

LAB 525The Image Bank/Getty Images

Use the InternetUse the Internet


Real-World QuestionThe symbols used for different elements sometimes are easy to figureout. After all, it makes sense for the symbol for carbon to be C and thesymbol for nitrogen to be N. However, some symbols aren’t as easy tofigure out. For example, the element silver has the symbol Ag. Thissymbol comes from the Latin word for silver, Argentum. How are sym-bols and names chosen for elements?

Make a Plan1. Make a list of particular elements you wish to study.

2. Compare and contrast these elements’ names to their symbols.

3. Research the discovery of these elements. Do their names matchtheir symbols? Were they named after a property of the element,a person, their place of discovery, or a system of nomenclature?What was that system?

Goals■ Research the names

and symbols of variouselements.

■ Study the methodsthat are used to nameelements and how theyhave changed throughtime.

■ Organize your data bymaking your own peri-odic table.

■ Study the history ofcertain elements andtheir discoveries.

■ Create a table of yourfindings and communi-cate them to other students.

Data Source

Visit gpscience.com/internet_lab for moreinformation on namingelements, elements’ sym-bols, and the discovery ofnew elements, and fordata from other students.

What’s in a name?

Tom Pantages

http://gpscience.com/internet_lab

Follow Your Plan1. Make sure your teacher approves your

plan before you start.

2. Visit the Web site provided for links todifferent sites about elements, their his-tory, and how they were named.

3. Research these elements.

4. Carefully record your data in your ScienceJournal.

Analyze Your Data1. Record in your Science Journal how the symbols for your elements were cho-

sen. What were your elements named after?

2. Make a periodic table that includes the research information on your elementsthat you found.

3. Make a chart of your class’s findings. Sort the chart by year of discovery for eachelement.

4. How are the names and symbols for newly discovered elements chosen?Make a chart that shows how the newly discovered elements will be named.

Conclude and Apply1. Compare your findings to those of your class-

mates. Did anyone’s data differ for the sameelement? Were all the elements in the periodictable covered?

2. Explain the system that is used to name thenewly discovered elements today.

3. Explain Some elements were assigned sym-bols based on their name in another language.Do these examples occur for elements discov-ered today or long ago?

LAB 527

Find this lab using the link below. Post yourdata in the table provided. Compare yourdata to those of other students. Combineyour data with those of other students tocomplete your periodic table with all of theelements.

gpscience.com/internet_lab

PhotoEdit, Inc.

http://gpscience.com/internet_lab

Picture this: It’s 1361. A ship from Norwayarrives at a Norwegian settlement inGreenland. The ship’s crew hopes to trade

its cargo with the people living there. The crewgets off the ship. They look around. The settlementis deserted. More than 1,000 people had vanished!

New evidence has shed some light on themysterious disappearance of the Norse settlers.The evidence came from a place on the GreenlandIce Sheet over 600 km away from the settle-ment. This part of Greenland is so cold thatsnow never melts. As new snow falls, the existing snow is buried and turns to ice.

By drilling deep intothis ice, scientists canrecover an ice core.

The core is made up of ice formed from snow-falls going way, way back in time.

By measuring the ratio of oxygen isotopes inthe ice core, scientists can estimate Greenland’spast air temperatures. The cores provide a detailedclimate history going back over 80,000 years.Individual ice layers can be dated much like treerings to determine their age, and the air bubblestrapped within each layer are used to learn aboutclimate variations. Dust and pollen trapped in theice also yield clues to ancient climates.

A Little Ice AgeBased on their analysis, scientists think the

Norse moved to Greenland during an unusuallywarm period. Then in the 1300s, the climatestarted to cool and a period known as the LittleIce Age began. The ways the Norse hunted andfarmed were inadequate for survival in this longchill. Since they couldn’t adapt to their coldersurroundings, the settlers died out.

Research Report Evidence seems to show that Earth iswarming. Rising temperatures could affect our lives. Researchglobal warming to find out how Earth may change. Share yourreport with the class.

For more information, visitgpscience.com/time

A CHILLING

STORY

SCIENCEAND

HISTORYSCIENCE

CAN CHANGE THE COURSE OF HISTORY!

A scientist inspects anice core sample from theGreenland Ice Sheet. The

samples are stored in afreezer at �36°C.

A CHILLING

STORY

Air bubbles and dirt trapped in iceprovide clues toEarth’s past climate.

(t)Roger Ressmeyer/CORBIS, (bl)Maria Stenzel/National Geographic Image Collection

http://gpscience.com/time

CHAPTER STUDY GUIDE 529gpscience.com/interactive_tutor

Structure of the Atom

1. A chemical symbol is a shorthand way ofwriting the name of an element.

2. An atom consists ofa nucleus made ofprotons and neutronssurrounded by anelectron cloud asshown in the figureto the right.

3. Quarks are particles of matter that make upprotons and neutrons.

4. The model of the atom changes over time.As new information is discovered, scientistsincorporate it into the model.

Masses of Atoms

1. The number of neutrons in an atom can becomputed by subtracting the atomic num-ber from the mass number.

2. The isotopes of an element are atoms ofthat same element that have different num-bers of neutrons. The figure below showsthe isotopes of hydrogen.

3. The average atomic mass of an elementis the weighted-average mass of the mixtureof its isotopes. Isotopes are named by usingthe element name, followed by a dash, andits mass number.

The Periodic Table

1. In the periodic table, the elements arearranged by increasing atomic numberresulting in periodic changes in proper-ties. Knowing that the number of pro-tons, electrons, and atomic number areequal gives you partial composition ofthe atom.

2. In the periodic table, the elements arearranged in 18 vertical columns, or groups,and seven horizontal rows, or periods.

3. Metals are found at the left of the periodictable, nonmetals at the right, and metalloidsalong the line that separates the metals fromthe nonmetals as shown below.

4. Elements are placed on the periodic table inorder of increasing atomic number. A newrow on the periodic table begins when theouter energy level of the element is filled.

Metals

Nonmetals

Metalloids

Use the Foldable that you made at the begin-ning of the chapter to help you review properties of atoms andthe periodic table.

http://gpscience.com/interactive_tutor

Fill in the blanks with the correct word or words.

1. Mendeleev created an organized table ofelements called the .

2. Two elements with the same number ofprotons but a different number of neutronsare called .

3. is the weighted-average mass ofall the known isotopes for an element.

4. The positively charged center of an atom iscalled the .

5. The particles that make up protons andneutrons are called .

6. A(n) is a horizontal row in theperiodic table.

7. The is the sum of the number ofprotons and neutrons in an atom.

8. In the current model of the atom, the elec-trons are located in the .

Choose the word or phrase that best answers thequestion.

9. In which state of matter are most of the ele-ments to the left of the stair-step line in theperiodic table?A) gas C) plasmaB) liquid D) solid

10. Which is a term for a pattern that repeats? A) isotopic C) periodicB) metallic D) transition

11. Which of the following is an element thatwould have similar properties to those ofneon?A) aluminum C) arsenicB) argon D) silver

12. Which of the following terms describesboron?A) metal C) noble gasB) metalloid D) nonmetal

13. How many outer-level electrons dolithium and potassium have?A) 1 C) 3B) 2 D) 4

14. Which of the following is NOT found inthe nucleus of an atom?A) proton C) electronB) neutron D) quark

15. The halogens are located in which group?A) 1 C) 15B) 11 D) 17

16. In which of the following states is nitrogenfound at room temperature?A) gas C) metalB) metalloid D) liquid

17. Which of the elements below is a shinyelement that conducts electricity and heat?A) chlorine C) hydrogenB) sulfur D) magnesium

18. The atomic number of Re is 75. Theatomic mass of one of its isotopes is 186.How many neutrons are in an atom of thisisotope?A) 75 C) 186B) 111 D) 261

530 CHAPTER REVIEW

atom p. 507atomic number p. 513average atomic mass p. 515 electron p. 507electron cloud p. 511electron dot diagram p. 522group p. 520isotope p. 514

mass number p. 513neutron p. 507nucleus p. 507period p. 523periodic table p. 516proton p. 507quark p. 507

gpscience.com/vocabulary_puzzlemaker

http://gpscience.com/vocabulary_puzzlemaker

CHAPTER REVIEW 531gpscience.com/chapter_review

19. As a star dies, it becomes more dense. Itstemperature rises to a point where Henuclei are combined withother nuclei. When thishappens, the atomicnumbers of the othernuclei are increased by 2because each gains thetwo protons contained inthe He nucleus. Forexample, Cr fuses withHe to become Fe. Copyand complete the conceptmap showing the firstfour steps in He fusion.

20. Copy and complete the concept map below.

21. Infer Lead and mercury are two pollutantsin the environment. From informationabout them in the periodic table, deter-mine why they are called heavy metals.

22. Explain why it is necessary to change mod-els as new information becomes available.

23. Infer Why did scientists choose carbon tobase the atomic mass unit? Which isotopeof carbon did they use?

24. Infer Ge and Si are used in making semi-conductors. Are these two elements in thesame group or the same period?

25. Explain Using the periodic table, predicthow many outer level electrons will be inelements 114, 116, and 118. Explain youranswer.

26. Infer Ca is used by the body to makebones and teeth. Sr-90 is radioactive. Ca issafe for people and Sr-90 is hazardous.Why is Sr-90 hazardous to people?

Interpreting Graphics

27. Solve One-Step Equations The atomic num-ber of Yttrium is 39. The atomic massof one of its isotopes is 89. How manyneutrons are in an atom of this isotope?

Use the table below for question 28.

28. Use Tables Use the information in Figure 10to determine how many electrons shouldbe in the 2nd, 3rd, and 4th energy levelsfor Argon, atomic number 18. Copy andcomplete the table above with the num-ber of electrons for each energy level.

Electrons per Energy Level

Energy Maximum Number Level of Electrons

1 2

2

3

4

He

+He

+He

+He

+He

Be

Atom

Electroncloud

Quarks

Neutrons

contains a

made of also made of

contains contains

contains an

contains

http://gpscience.com/chapter_review

Record your answers on the answer sheetprovided by your teacher or on a sheet of paper.

1. Atoms of different elements are differentbecause they have different numbers ofwhat type of particle?A. electrons C. protonsB. photons D. neutrons

2. Which group of elements on the periodictable do not combine readily with otherelements? A. Group 1 C. Group 17B. Group 2 D. Group 18

Use the illustration below to answer questions 3 and 4.

3. What is the name by which the elementsalong the stair-step line, darkly shaded onthe periodic table shown above, are known?A. lanthanides C. metalsB. metalloids D. nonmetals

4. Which of the regions shown on the peri-odic table contains mostly elements that aregases at room temperature?A. region 1 C. region 3B. region 2 D. region 4

5. Which scientist proposed the idea thatatoms make up all substances?A. Aristotle C. DemocritusB. Dalton D. Galileo

Use the table below to answer questions 6 and 7.

6. The table above lists properties of someelements. Which element in the table hasa complete outer energy level?A. carbon C. neonB. oxygen D. sodium

7. Which element would you expect to belocated in Group 1 of the periodic table?A. oxygen C. sodiumB. neon D. chlorine

8. How many quarks have been found to exist? A. six C. tenB. eight D. twelve

9. The element nickel has five naturally occurring isotopes. Which of the followingdescribes the relationship of these isotopes?A. same mass, same atomic number B. same mass, different atomic number C. different mass, same atomic number D. different mass, different atomic number

532 STANDARDIZED TEST PRACTICE

Partial Credit Never leave any open ended answer blank.Answer each question as best as you can. Often, you canreceive partial credit for partially correct answers.

Question 20 If you have some of the particles mixed up, try towrite as much as you remember.

ElementElectrons in aNeutral Atom

Electrons inOuter Energy Level

Carbon 6 4

Oxygen 8 6

Neon 10 8

Sodium 11 1

Chlorine 17 7

STANDARDIZED TEST PRACTICE 533gpscience.com/standardized_test

Record your answers on the answer sheetprovided by your teacher or on a sheet of paper.

10. According to the periodic table, an atomof lead has an atomic number of 82. Howmany neutrons does lead-207 have?

11. About three out of four chlorine atomsare chlorine-35, and about one out of fourare chlorine-37. What is the averageatomic mass of chlorine?


12. The electron dot diagram above showshow a sodium atom, Na, combines with achlorine atom, Cl, to form sodium chlo-ride. What do the � and the � symbolsindicate in the diagram?

13. What do the dots around the chlorineatom indicate?

14. Why isn’t the mass of the electronincluded in the mass of an atom on theperiodic table?

15. What determines the chemical propertiesof an element?

16. What property of radioactive isotopes canscientists use to determine the age ofbones or rock formations?

17. The atomic mass for silicon is listed as28.09 amu on the periodic table. A studentclaims that no silicon atom has thisatomic mass. Is this true? Explain why orwhy not.

Record your answers on a sheet of paper.


18. The illustration above shows the currently accepted model of atomic structure. Describe this model.

19. Compare and contrast the model shownabove with Bohr’s model of an atom.

20. Describe the composition of protons,neutrons, and electrons.

21. How can you use the periodic table todetermine the average number of neu-trons an element has, even though thenumber of neutrons is not listed?

22. Describe the concept of energy levels andhow they relate to the placement of ele-ments on the periodic table.

23. Explain the importance of the rows in theperiodic table’s organization of elements.

24. Describe how Dalton’s modernization ofthe ancient Greek’s ideas of element, atom,and compound provided a basis forunderstanding chemical reactions. Give an example.

Nucleus

Electron cloud

Cl �

Na �

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Chapter 17: Properties of Atoms and the Periodic Tablebkscience.weebly.com/uploads/1/6/3/2/16325492/chap... · 3 The Periodic Table ... composed of tiny particles called atoms