Atomic StructureAtomic StructureCh. 5.1 & 5.2Ch. 5.1 & 5.2

Gotta start Gotta start somewheresomewhereLe t ’

s go backward in order to go forward

What was that all about?

• To study atoms and their interactions, we need to revisit something we studied earlier this year

•Matter and mass

Matter and MassMatter and Mass

So matter is made So matter is made of… of…

ELEMENTS!ELEMENTS!

Pure substancesPure substances that that cannot be broken down cannot be broken down chemically into simpler chemically into simpler kinds of matter kinds of matter

More than 100 elements More than 100 elements (92 naturally occurring)(92 naturally occurring)

AboutAbout 2525 of the 92 of the 92 natural elements are natural elements are essential to lifeessential to life

So matter is made So matter is made of… of…

ELEMENTS!

Pure substances that cannot be broken down chemically into simpler matter

More than 100 elements (92 naturally occurring)

About 25 of the 92 natural elements are essential to life

What about the rest of What about the rest of them?them?

Many used for new technology

Platinum: Catalytic converters, fuel cells, electrodes

Indium: Solar panels

Gallium: LED’s, laser diodes, photodetectors

Tantalum: Microchips, new technologies

ATOMSATOMSThe simplest particle of an element that retains all the properties of that element

Atoms of each element Atoms of each element of have unique of have unique properties that properties that determine how that determine how that element behaves during element behaves during chemical reactionschemical reactions

What do we know about What do we know about ATOMS?ATOMS?

Dalton’s Atomic Theory Dalton’s Atomic Theory summarizes the key ideassummarizes the key ideas

1. All elements are composed 1. All elements are composed of tiny indivisible particles of tiny indivisible particles called atoms*called atoms*

2. Atoms of the same element 2. Atoms of the same element are identical. Each element is are identical. Each element is made of one type of atom.made of one type of atom.

What do we know about What do we know about ATOMS?ATOMS?

Dalton’s Atomic Theory summarizes the key ideas

3. Atoms of different elements can mix together physically or chemically combine to make compounds

4. Chemical reactions occur when atoms are separated, joined or rearranged. Atoms of one element are never changed into atoms of another element.

How big How big (or small) (or small) is an is an atom?atom?

Cell Size and Scale – University of Utah Genetics

If a penny was made of pure copper, there would be approximately 2.4x1022 atoms in that one coin.

100 million copper atoms lined up in a row would cover 1 cm of distance

How big How big (or small) (or small) is an is an atom?atom?

A typical human hair is approximately 1 million carbon atoms wide

100x magnification 400x magnification

Is it possible to Is it possible to see atoms?see atoms?

Yes, with very advanced microscopesYes, with very advanced microscopes

STM – Scanning Tunneling MicroscopeSTM – Scanning Tunneling Microscope

Pb atoms on silicon surface

““The STM works by scanning a very sharp The STM works by scanning a very sharp metal wire tip over a surface. By bringing metal wire tip over a surface. By bringing the tip very close to the surface, and by the tip very close to the surface, and by applying an electrical voltage to the tip or applying an electrical voltage to the tip or sample, we can image the surface at an sample, we can image the surface at an extremely small scale – down to resolving extremely small scale – down to resolving individual atoms.” individual atoms.” Nanoscienceinstruments.comNanoscienceinstruments.com

Atomic StructureAtomic StructureThree particles make up atomsThree particles make up atoms

Protons - Mass of 1 amu, Charge of +1Protons - Mass of 1 amu, Charge of +1

Neutrons – Mass of 1 amu, No charge Neutrons – Mass of 1 amu, No charge (neutral)(neutral)

Electrons – No mass, Charge of -1Electrons – No mass, Charge of -1

Atomic StructureAtomic StructureThree particles make up atomsThree particles make up atoms

Protons - Mass of 1 amu, Charge of +1Protons - Mass of 1 amu, Charge of +1

Neutrons – Mass of 1 amu, No charge (neutral)Neutrons – Mass of 1 amu, No charge (neutral)

Electrons – No mass, Charge of -1Electrons – No mass, Charge of -1

Atoms have two regions: Atoms have two regions: The nucleusThe nucleus in in the center, and the center, and The outer energy levelsThe outer energy levels

Protons and Neutrons are found in the Protons and Neutrons are found in the nucleus, Electrons are found in the nucleus, Electrons are found in the outer energy levelsouter energy levels

Atomic StructureAtomic StructureDiagram of a Carbon Atom

Nuc

leus

Ene

rgy

Leve

ls

Atomic Structure Atomic Structure Subatomic Particles

Protons Neutrons Electrons

Location Nucleus Nucleus Electron Cloud (energy levels)

Charge + (positive) 0, neutral -, negative

Mass Appx 1.7X10-24 grams or 1amu

Appx 1.9 X10-24 grams or 1 amu

0

How to determine the number in each atom

Atomic # Atomic Mass-Atomic #

Same as # of Protons if atom has no charge

Special Fxn Gives Atoms their identity

Different #s within the same type of atom creates isotopes

Determine chemical reactivity

Atom TerminologyAtom Terminology

The The Atomic Number Atomic Number for an element for an element is the number of protons in an atom of is the number of protons in an atom of that element. that element.

Hydrogen atoms all have one proton, Hydrogen atoms all have one proton, so the Atomic Number for Hydrogen is so the Atomic Number for Hydrogen is 11

Atoms with different atomic numbers Atoms with different atomic numbers will be from different elementswill be from different elements

Atom TerminologyAtom TerminologyMass number is the total Mass number is the total number of protons and number of protons and neutrons in an atomneutrons in an atom

# of neutrons = mass number # of neutrons = mass number – # of protons (atomic – # of protons (atomic number)number)

Terminology ContinuedTerminology ContinuedIsotopes: Atoms of the same element that have different numbers of neutrons

IsotopesIsotopesAtoms

Atoms of the same element that vary in the number of ___________

(atomic # same, atomic mass varies)

neutrons

IsotopesIsotopes1

H

1

2

H

1

3

H

1

Potassium in a banana: 39K (93.25%), 40K (6.7302%) and 41K (0.0117%)

Atomic # 19

99.98% 0.015% trace

19p 20n 19e

19p 21n 19e 19p 22n 19e

Why do atomic masses Why do atomic masses (mass #) have decimal (mass #) have decimal

places?places?Most elements exist as mixtures of Most elements exist as mixtures of two or more isotopes. two or more isotopes.

Atomic mass Atomic mass is the average mass is the average mass of all of the isotopes of given of all of the isotopes of given element.element.

Determine the Mass # of Determine the Mass # of Carbon Carbon

C-12 98.89%

C-13 1.11%

C-14 trace

12.011C6

12 x .9889 = 11.8668

13 x .0111= 0.1443

+

12.0111

The ElectronsThe ElectronsTravel at very high speedsTravel at very high speeds at various at various distances distances (energy levels)(energy levels) from the nucleus from the nucleus

Electrons in the same energy level are Electrons in the same energy level are approximately the same distance from the approximately the same distance from the nucleusnucleus

Outer energy levels have more energy than Outer energy levels have more energy than inner levelsinner levels

Each levelEach level holds only a holds only a certain number of certain number of electronselectrons

Remember 2 8 8 !

Subatomic ParticlesSubatomic Particles

ProtonsProtons

NeutronsNeutrons

ElectronsElectrons

Drawing AtomsDrawing Atoms

Atomic # Atomic #

Atomic MassAtomic Mass

(Mass #)(Mass #)19

F

9

1

H

1

12C

6

Atoms1P0N

1e

9P10N 2

e 7e

6P6N 2

e4e

16O8

Draw These Atoms

7Li3

31P15

15P16N

2e

8e5e

8P8N

3P4N

2e

1e

2e

6e

Periodic TablePeriodic Table1 2

3 4 5 6

•Elements arranged on a periodic table by their atomic numbers

7 8

Periodic Periodic TableTable

Period Tells the number of energy levels

Fam

ily Tells the number of outermost electrons

# of outermost electrons

CompoundsCompoundsMost elements do not exist Most elements do not exist by themselvesby themselves

Readily combine with other Readily combine with other elementselements in a predictable in a predictable fashionfashion

CompoundCompound Pure substance Pure substance made up made up of atoms of two or more of atoms of two or more elementselementsProportion of atoms are Proportion of atoms are always fixedalways fixedIonic or covalently bondedIonic or covalently bonded

Chemical formulaChemical formula: the : the kindkind and and proportion proportion of atoms of of atoms of each element in a compound each element in a compound

EX: HEX: H22OO H2O

Molecules: two or more elements covalently bonded (the elements can be the same (O2) or different (CO2)

SAME!

Let’s welcome our friend…

GLUCOSE!

Atoms of different elements

Blue: CarbonRed: OxygenGray: Hydrogen

MoleculeMolecule

The simplest part of a The simplest part of a substance that retains all of substance that retains all of the properties of the the properties of the substance and exists in a free substance and exists in a free statestate

Some can be very Some can be very LARGELARGE and and COMPLEXCOMPLEX

Key Difference Between Key Difference Between Molecules and CompoundsMolecules and Compounds

Compounds: Made of two or more Compounds: Made of two or more different types of atomsdifferent types of atoms

Molecules: Made of the same or Molecules: Made of the same or different types of atomsdifferent types of atoms

Chemical FormulasChemical Formulas 6CO2 + 6H2O C6H12O6 + 6O2When have we seen this before?What are the pieces?What exactly is this formula telling us?

Chemical equationsChemical equations represent represent chemical reactionschemical reactions

A ____________ represents the A ____________ represents the number of number of moleculesmolecules involved in involved in the reactionthe reaction

A _____________represents the A _____________represents the number of number of atomsatoms in each molecule in each molecule

coefficient

subscript2H2O

2H2O

Chemical FormulasChemical Formulas 6CO2 + 6H2O C6H12O6 + 6O2

How many atoms of carbon are in a molecule of glucose? (subscript)

How many water molecules are necessary to make a molecule of glucose? (coefficient)

6

6

Chemical equationsChemical equations represent represent chemical reactionschemical reactions

Chemical ReactionsChemical Reactions: Atoms in an existing : Atoms in an existing substance are substance are rearrangedrearranged to form a new to form a new substance. substance.

Chemical bonds in the reactants are Chemical bonds in the reactants are brokenbroken, and , and new bonds are new bonds are formedformed to make the products. to make the products.

A A Chemical EquationChemical Equation represents the chemical represents the chemical reaction that converts the original substances reaction that converts the original substances (original forms of matter) into new substances (original forms of matter) into new substances (new forms of matter)(new forms of matter)

22HH22 + 0 + 02222HH22OOReactants

Products

Chemical equationsChemical equations represent represent chemical reactionschemical reactions

A A Chemical EquationChemical Equation represents the represents the chemical reaction that converts the chemical reaction that converts the original substances (original forms of original substances (original forms of matter) into new substances (new matter) into new substances (new forms of matter)forms of matter)

Reactants

Products 6CO2 + 6H2O C6H12O6 + 6O2

• The number of each kind of atom must be the same in both the reactants and products

An attraction between An attraction between atoms that forms as a atoms that forms as a result of the sharing or result of the sharing or complete transfer of complete transfer of electrons.electrons.

Atoms tend to reactAtoms tend to react (combine) with other (combine) with other atoms atoms in order to become in order to become more stablemore stable (undergo (undergo chemical reactions)chemical reactions)

Stability = full outer electron Stability = full outer electron levellevel

Chemical Bonds

What about the What about the family farthest to family farthest to

the right?the right?The noble gases have a full outer electron shell and thus do not want to react with other elements.

They are stable!

Ionic BondsIonic BondsSome atoms become stable by Some atoms become stable by becoming ions--- becoming ions--- losing or gaining losing or gaining electronselectrons

Atoms that Atoms that lose electronslose electrons are called are called positive ions _____________positive ions _____________

Atoms thatAtoms that gain electrons gain electrons are calledare called negative ions __________negative ions __________

cations

anions

Because Because positive and negative positive and negative electrical charges attractelectrical charges attract each other each other

ionic bondsionic bonds form form

Other ionic compounds: CaCl2 KBr

MgF2

The The physical and physical and chemical propertieschemical properties of a of a compound differ from compound differ from the physical and the physical and chemical properties of chemical properties of the individual elements the individual elements that compose itthat compose it

Sodium- soft, silvery white, highly reactive metal

Will Kill You

Chlorine- yellowish green , non metal, gas

Will Kill You

Sodium Chloride-

Table Salt

YUM

Example of emergent properties

Emergent property: Characteristic of a system not observed in any of its individual components.

Other example

Alk

alin

e E

art

h

Meta

ls

Alk

ali

Meta

ls

Nobel G

ase

s

Halo

gens

Chalc

ogens

Covalent BondsCovalent BondsFormed when two Formed when two atoms atoms share one or share one or more pairs of more pairs of electronselectrons

Octet RuleOctet Rule

Covalent v. Ionic Covalent v. Ionic BondsBondsCovalent Ionic

Inter-element interaction

Sharing of electrons to make full outer electron shells

Transfer of electrons to make full outer electron shells

Reason for happening

Increased stability

Increased stability

Attraction is the result of

Dependence on other atom for electron sharing

+/- charges of ions

Typical Example

NaCl H2O

Bonds make Compounds or molecules

Compounds