chapter 4 atomic structure and the periodic table

Chapter 4Chapter 4

Atomic Structureand

The Periodic Table

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Democritus’s Democritus’s Greek PhilosopherGreek Philosopher

Democritus’s Atomic Democritus’s Atomic TheoryTheory

Atoms are indivisible and indestructible.

Each substance had a different type of atom.

Liquid – smooth and roundSolid – rough and prickly

Who’s Next?Who’s Next?

Late 1700’s - John Dalton- England.Teacher- summarized results of his

experiments and those of others.Dalton’s Atomic TheoryCombined ideas of elements with that

of atoms.

John Dalton (1766-1844)John Dalton (1766-1844)

Dalton’s Atomic TheoryDalton’s Atomic Theory All matter is made of tiny indivisible

particles called atoms. Atoms of the same element are identical,

those of different atoms are different. Atoms of different elements combine in

whole number ratios to form compounds. Chemical reactions involve the

rearrangement of atoms. No new atoms are created or destroyed.

Just how Small is an Atom?Just how Small is an Atom?

Think of cutting a piece of lead into smaller and smaller pieces

How far can it be cut?An atom is the smallest particle

of an element that retains the properties of that element

Parts of AtomsParts of Atoms

J. J. Thomson - English physicist. 1897

Made a piece of equipment called a cathode ray tube.

It is a vacuum tube - all the air has been pumped out.

J.J. Thompson (1856 – 1940)J.J. Thompson (1856 – 1940)

Thompson 1897Thompson 1897

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Vacuum tube

Metal Disks

Thomson’s ExperimentThomson’s Experiment

Voltage source

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Thomson’s ExperimentThomson’s Experiment

Voltage source

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Thomson’s ExperimentThomson’s Experiment

Voltage source

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Passing an electric current makes a Passing an electric current makes a beam appear to move from the beam appear to move from the negative to the positive end.negative to the positive end.

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Passing an electric current makes a Passing an electric current makes a beam appear to move from the beam appear to move from the negative to the positive end.negative to the positive end.

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Passing an electric current makes a Passing an electric current makes a beam appear to move from the beam appear to move from the negative to the positive end.negative to the positive end.

Thomson’s ExperimentThomson’s Experiment

Voltage source

+-

Passing an electric current makes a Passing an electric current makes a beam appear to move from the beam appear to move from the negative to the positive end.negative to the positive end.

Thomson’s ExperimentThomson’s Experiment

Voltage source

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Voltage source

Thomson’s ExperimentThomson’s Experiment

By adding an electric field.

Voltage source

Thomson’s ExperimentThomson’s Experiment

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-

Voltage source

Thomson’s ExperimentThomson’s Experiment

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-

Voltage source

Thomson’s ExperimentThomson’s Experiment

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-

Voltage source

Thomson’s ExperimentThomson’s Experiment

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-

Voltage source

Thomson’s ExperimentThomson’s Experiment

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-

Voltage source

Thomson’s ExperimentThomson’s Experiment

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-

Other particlesOther particles

Proton - positively charged pieces 1840 times heavier than the electron – by E. Goldstein

Neutron - no charge but the same mass as a proton – by J. Chadwick

Where are the pieces?

Ernest Rutherford (1871-Ernest Rutherford (1871-1937)1937)

Rutherford Rutherford

Rutherford’s experimentRutherford’s experiment

Ernest Rutherford -English physicist. (1910)

Plum Pudding model of the atom.Wanted to see how big they are.Used radioactivity.Alpha particles.Shot them at gold foil.

Rutherford’s experimentRutherford’s experiment

When an alpha particle hits a fluorescent screen, it glows.

Here’s what it looked like.

Lead block

Uranium

Gold Foil

Fluorescent Screen

What he expected…

Because…..

He thought the mass was evenly distributed in the atom.

Since he thought the mass was evenly distributed in the atom.

What he got…

How he explained it

Atom is mostly empty.Small dense, positive

piece at center.Alpha particles are

deflected by it if they get close enough.

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Worksheet: 4.1Due: 10/24/08

Homework 4-1Homework 4-1

Matter and AtomsMatter and Atoms

Nucleus

p+ Protons

n Neutrons

e-

Electrons

Atomic NumberAtomic Number

The number of The number of protons protons in an atom.in an atom.

In a neutral atomIn a neutral atom# of protons = # of electrons# of protons = # of electrons

Atomic MassAtomic MassThe number of The number of

protons and neutrons protons and neutrons in an atom.in an atom.

# of neutrons =# of neutrons =Atomic mass - # of protonsAtomic mass - # of protons

Average Atomic MassThe average of the atomic mass

of all the isotopes of that element. 

IsotopesAtoms of the same element with

different number of neutrons.

1P+2N

1e-

Tritium

Average Atomic Mass for H = 1.00794

1P+1N

1e-

Deuterium

1P+0N

1e-

Protium

15

30.96376Phosphorus

PAtomic Number(# of Protons)

Symbol

AverageAtomic Mass

(31)

Name

Element: Phosphorus

# of Protons: 15

15p+

# of Neutrons: 31 –15 = 16

16nº

# of Electrons: 15

)2e-

)8e-

)5e-

Homework 4-2Homework 4-2

Worksheet: 4-2Due: 10/24/08

Bohr 1913Bohr 1913

Planetary ModelPlanetary Model

Energy LevelsEnergy Levels

The possible energies that an The possible energies that an electron in an atom can have are electron in an atom can have are

called called Energy Levels.Energy Levels.

Energy LevelsEnergy Levels

Nucleus

1st Level

2nd Level

3rd Level

4th Level

ee--

Energy

Energy

Evidence of Energy levelsEvidence of Energy levels

The energy given off by an electron is in the form of light.

Specific element give off specific colors.

Spectral Analysis

Evidence of Energy levelsEvidence of Energy levels

Electron CloudElectron CloudModel 1926Model 1926

nucleus

Electron CloudElectron CloudModel 1926Model 1926

nucleusScientist use the electron cloud model to describe the possible locations of

electrons around the nucleus.

Atomic OrbitalsAtomic Orbitals

In each energy level the electrons can have certain orbits that they can take.

This a probability of where the electron can be found.

Electron Cloud ModelElectron Cloud Model

Nucleus

1st Level2e-

2nd Level8e-

3rd Level18e-

Atomic OrbitalsAtomic Orbitals

Energy

Level

Number of

Orbitals

Maximum Number of Electrons

1 1 22 4 83 9 184 16 32

)2e-

)8e-

)18e-

)32e-

Number of ElectronsNumber of Electrons

Electron ConfigurationElectron Configuration

Where the electrons are in the orbitals of the atom.

The most stable configuration is the one in which the electrons are in orbitals with the lowest energy.

Lowest Energy of the electrons is called the Ground State.

Element: Phosphorus

# of Protons: 15

15p+

# of Neutrons: 31 –15 = 16

16nº

# of Electrons: 15

)2e-

)8e-

)5e-

Homework 4-3Homework 4-3

Worksheet: 4-3Due: 10/28/08Test: 10/30/08

Democritus’s Atomic Democritus’s Atomic TheoryTheory

Indivisible

Indestructible

Each substance - different type atom.

Dalton’s Atomic TheoryDalton’s Atomic Theory

Billiard Ball ModelBilliard Ball Model

Dalton’s Atomic TheoryDalton’s Atomic Theory

Indivisible particles called atoms. Same elements - identical atoms.

Whole number ratios - compounds.

CO2 CO Chemical reactions …

… rearrangement of atoms.

Voltage source

Thomson’s ExperimentThomson’s Experiment

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Existence of Charged ParticleExistence of Charged ParticlePositive and NegativePositive and Negative

Plum Pudding ModelPlum Pudding Model

Rutherford’s Experiment

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Atoms have:

Mostly empty.

Small dense, + piece at center.

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Bohr Bohr Planetary ModelPlanetary Model

Electrons in Energy LevelsElectrons in Energy Levels

Electron Cloud ModelElectron Cloud Model

nucleus

Matter and AtomsMatter and Atoms

Nucleus

p+ Protons

n0Neutrons

e-

Electrons

14

26.982Aluminum

SiAtomic Number(# of Protons)

AverageAtomic Mass(p+ + n0 = 27) AKA - Mass Number

p+ = 14

e- = p+ = 14

n0 = Mass - p+ n0 = 27 – 14 = 13

p+ = 14 e- = 14 n0 = 13

28

4

Atomic OrbitalAtomic Orbital

A region of space around the nucleus where an electron is like to be found.

Contains 2 electrons.

28

4

27

5

GroundState

ExcitedState

IsotopesAtoms of the same element with

different number of neutrons.

Cl - 35 Cl - 37p+ - 17 p+ - 17n0 - 18 n0 - 20

Average Atomic Mass – 35.453

Element #2 Element #3

Element #1 Element #1

Element #3: ________________ Color: ____________

Element #4: ________________ Color: ____________

Spectrum

Spectrum