chapter 4 atomic structure and the periodic table
TRANSCRIPT
Chapter 4Chapter 4
Atomic Structureand
The Periodic Table
Anc
ient
A
ncie
nt
Gre
eks
Gre
eks
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
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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
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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
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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