Atomic Theory Atomic Theory and Structureand Structure

The Theory of the Atom• ___________, a Greek teacher in the 4th Century B.C., first suggested the idea of the atom.

•All matter is composed of tiny, _________ particles called _______

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Democritus

indivisibleatoms

In 1803, ____________ In 1803, ____________ studied experiments and studied experiments and concluded that the concluded that the properties of matter properties of matter could be explained in terms could be explained in terms of _____.of _____.

John Dalton

atoms

Dalton’s _____________ had 4 Dalton’s _____________ had 4 pointspoints

1.1. Each ________ is composed of Each ________ is composed of extremely small particles called extremely small particles called atoms (which are indivisible).atoms (which are indivisible).

2.2. All atoms of a given element All atoms of a given element are _______, but they differ from are _______, but they differ from those of any other those of any other element.element.

Atomic Theory

element

identical

3. Atoms are neither 3. Atoms are neither ________ nor ________ in ________ nor ________ in any chemical reaction.any chemical reaction.

4. A given _________ 4. A given _________ always has the same always has the same relative numbers and relative numbers and kinds of atoms.kinds of atoms.

Atomic Theory Continued…

createddestroy

edcompound

Dalton’s Model of the AtomHe believed the atom

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The AtomThe Atom

Is composed of an Is composed of an __________ is an __________ is an atom.atom.

The atom is made The atom is made up of three up of three ___________ ___________ particles: ________,particles: ________,

___________ and ___________ and ____________________

ELEMENT

SUBATOMIC

PROTONS

NUETRONS

ELECTRONS

Michael Faraday Michael Faraday 18931893Atoms contain Atoms contain particles that have an particles that have an __________ charge__________ charge

electrical

ElectronElectronDiscovered in 1897 by Discovered in 1897 by ____________________

Has a _________ chargeHas a _________ charge

JJ Thomsonnegative

Thomson also thought in addition to the negatively charged electrons, there must be something with a __________ charge because the overall charge of the atom is ___________

positive

neutral

Plum Pudding Model

Ernest RutherfordErnest RutherfordPerformed Gold Foil Experiment in Performed Gold Foil Experiment in ______.______.

He shot _______ particles (very small, He shot _______ particles (very small, dense, fast and positively charged dense, fast and positively charged particles) at a thin layer of gold foil.particles) at a thin layer of gold foil.

1909alpha

Alpha particles source

Gold foil

Detector screenAlpha particles

Because of Thomson’s Atom

But, what he found was But, what he found was this…this…

Most of the alpha particles went straight through but a tiny amount were deflected

In the atom there was something dense enough to deflect the alpha particles = ________

Like this…

nucleus

Importance of Rutherford’s Importance of Rutherford’s ExperimentExperiment

1. Showed most of the atom is 1. Showed most of the atom is made up of empty __________made up of empty __________

2. Proved the atom had a small, 2. Proved the atom had a small, dense area in its center known dense area in its center known now as the _____________now as the _____________

3. The nucleus has a _________ 3. The nucleus has a _________ charge (must have __________ in it)charge (must have __________ in it)

nucleuspositive

protons

space

Rutherford’s Atom

Other important Other important discoveries……discoveries……

NeutronNeutronDiscovered in 1932 by Discovered in 1932 by

________________________Has no charge (i.e. It is Has no charge (i.e. It is

______)______)

neutral

James Chadwick

ProtonProtonDiscovered in ______ by E. Discovered in ______ by E. GoldsteinGoldstein

Has a ________ chargeHas a ________ charge

1886

positive

Bohr ModelBohr Model

Modern Atomic StructureModern Atomic Structure The atom is made up of 2 The atom is made up of 2

parts/sectionsparts/sections

(1) The _________ --- (in the (1) The _________ --- (in the center of the atomcenter of the atom; contains ; contains protons and neutronsprotons and neutrons))

(2) The _____________ --- (2) The _____________ --- (surrounds the nucleus)(surrounds the nucleus)

nucleus

electron cloud

Nucleus (protons and neutrons)Electrons cloud (electrons)

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The AtomThe AtomThe smallest particle of an ________ is an atom.

The atom is made up of three _________ particles: _______, _________, and _______

element

subatomicproto

nsneutronselectro

ns

Particle

Charge

Location

Mass (g)

Mass(amu

)Proto

n(P )

Positive

Nucleus

1.673 x 10

1

Neutron

(N°)

Neutral (No charg

e)

Nucleus

1.675 X 10

1

Electron

(E )

Negative

Around Nucleus

9.109 x 10

11837

(0)

+

-

-24

-24

-28

Protons

Overall ChargeOverall ChargeThe overall charge of an The overall charge of an atom is ____(neutral)atom is ____(neutral)

So, the number of protons So, the number of protons must _______ the number of must _______ the number of electronselectrons

So, the atomic number So, the atomic number also tells us the number of also tells us the number of _______________in an atom_______________in an atom

0

equal

electrons

Mass NumberMass NumberThe mass of an atomThe mass of an atomMeasured in ________Measured in ________Equal to the total Equal to the total number of __________ number of __________ and __________and __________

AMU’s

protonsneutrons

How to determine……..How to determine……..1) The number of protons = 1) The number of protons = Look at ______________Look at ______________

2) The number of electrons = 2) The number of electrons = Look at ______________(number Look at ______________(number of protons = number of of protons = number of electrons)electrons)

3) The number of neutrons = 3) The number of neutrons = ___________ – atomic number ___________ – atomic number

atomic numberatomic number

Mass number

Practice ProblemsPractice Problems1) Find the # of e1) Find the # of e--, p, p++ and n and n00 for for

sodium. (mass # = 23)sodium. (mass # = 23)

2) Find the # of e2) Find the # of e--, p, p++ and n and n00 for for uranium. (mass # = 238)uranium. (mass # = 238)

3) What is the atomic # and mass 3) What is the atomic # and mass # for the following atom? # for the following atom?

# e# e-- = 15; # n = 15; # n0 0 = 16= 16

IonsIonsWhen an atom loses or When an atom loses or gains one or more gains one or more ________, it acquires a net ________, it acquires a net electrical charge and is electrical charge and is called an ____. called an ____.

2 types of ions:2 types of ions:1) Anion1) Anion2) Cation2) Cation

electrons

ion

Anions and CationsAnions and Cations____________: An ion that has ____________: An ion that has more electrons than protons has more electrons than protons has a ___________ charge. a ___________ charge. **(Gained Electrons)** **(Gained Electrons)**

____________:An ion that has ____________:An ion that has fewer electrons that protons has fewer electrons that protons has a _____________ charge. a _____________ charge.

**(Lost Electrons)****(Lost Electrons)**

Anionnegati

ve

Cationpositive

Determining the Charge Determining the Charge of an Ionof an Ion

# of protons - # of # of protons - # of electronselectrons

Ion NotationIon Notation

Practice ProblemsPractice Problems1) A neutral magnesium atom (atomic 1) A neutral magnesium atom (atomic number 12) has 12 protons and 12 number 12) has 12 protons and 12 electrons. If the atom loses 2 electrons, electrons. If the atom loses 2 electrons, what is the charge of the resulting ion?what is the charge of the resulting ion?

2) How many electrons would be found in 2) How many electrons would be found in the ion Othe ion O2-2-??

3) If an ion has 28 protons and 26 3) If an ion has 28 protons and 26 electrons, what is its charge? What is electrons, what is its charge? What is its symbol (including charge)?its symbol (including charge)?

IsotopesIsotopesAn isotope refers to atoms An isotope refers to atoms that have the same # of that have the same # of ______, but they have a ______, but they have a different # of _______. different # of _______.

Because of this, they have Because of this, they have different ____ #’s (or different ____ #’s (or simply, different ______.) simply, different ______.)

protons neutro

ns

massmasses

Exm:Exm: (1) Carbon-12 & Carbon- (1) Carbon-12 & Carbon-13 13

(2) Chlorine-35 & Chlorine-(2) Chlorine-35 & Chlorine-3737

(The # shown after the name is the (The # shown after the name is the mass #.)mass #.)

For each example, the elements For each example, the elements have identical ______ #’s, but have identical ______ #’s, but different _____ #’sdifferent _____ #’s

atomicmas

s

Isotopes cont…Isotopes cont…

In nature, elements are In nature, elements are found as a _______________ found as a _______________ of all their isotopesof all their isotopes

The isotopes are found in The isotopes are found in the same the same ____________________________________

mixture

percentage

More Practice ProblemsMore Practice Problems1) Find the # e1) Find the # e--, p, p++ and n and n00 for Xe-131. for Xe-131.

2) Find the # e2) Find the # e--, p, p++ and n and n00 for Cu for Cu

3) Write a shorthand way to represent 3) Write a shorthand way to represent the following isotope:the following isotope:

# e# e-- = 1 # n = 1 # n00 = 0 = 0 # p# p++ = 1 = 1

63

29

Atomic MassAtomic MassThe atomic masses listed in the The atomic masses listed in the Periodic Table are a Periodic Table are a “_____________” of all the “_____________” of all the isotopes of the element.isotopes of the element.weighted

average

Practice ProblemsPractice Problems(1) Mrs. Smith’s geometry semester grades are calculated (1) Mrs. Smith’s geometry semester grades are calculated

using a weighted average of three category scores: using a weighted average of three category scores:

Tests/Quizzes= 30% of your gradeTests/Quizzes= 30% of your grade

Homework/Participation=60% of your gradeHomework/Participation=60% of your grade

Semester Exam= 10% of your gradeSemester Exam= 10% of your grade If a student had the following scores, what would they If a student had the following scores, what would they

receive for the semester?receive for the semester?

Tests/Quizzes= 80 (B-)Tests/Quizzes= 80 (B-)

Homework/Participation= 60 (D-)Homework/Participation= 60 (D-)

Semester Exam=65 (D)Semester Exam=65 (D)

Step (1):Step (1): Multiply each score by the % that Multiply each score by the % that it is weighted.it is weighted.

Step (2):Step (2): Add these products up, and that is Add these products up, and that is the weighted average! the weighted average!

A “normal average” would be calculated A “normal average” would be calculated by simply adding the raw scores together by simply adding the raw scores together and dividing by 3…and dividing by 3…

80 + 60 + 65 = 205 80 + 60 + 65 = 205 ÷ 3 = 68.3 = D÷ 3 = 68.3 = D

+

(2) In chemistry, chlorine has 2 isotopes:(2) In chemistry, chlorine has 2 isotopes:

Cl-35 (75.8% abundance) Cl-35 (75.8% abundance)

Cl-37 (24.23 % abundance) Cl-37 (24.23 % abundance)

What is the weighted average atomic mass What is the weighted average atomic mass of chlorine?of chlorine?

(3) Oxygen has 3 isotopes: (3) Oxygen has 3 isotopes:

O-16 (99.76%) O-17 (0.037%) O-16 (99.76%) O-17 (0.037%)

O-18 (0.2%)O-18 (0.2%)

EstimateEstimate oxygen’s average atomic mass. oxygen’s average atomic mass.

+