Diapositive 1

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Chemistry 101
Chapter 11 Modern Atomic Theory
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Structure of atom

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Rutherfords model
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e-

(Source of ? particles)
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Electromagnetic radiation
Energy is transferred by light.
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Electromagnetic radiation
A wave characterized by three properties
Wavelength
Wave
Frequency
Speed
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Electromagnetic radiation
Wavelength (?) distance from one wave peak to
the next.
Frequency (?) number of peaks that pass a given
point in one second.
c
?
c speed of light 3.0 108 m/s
?
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Electromagnetic radiation
longer ? ? lower ? shorter ? ? higher ?
Electromagnetic spectrum
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Electromagnetic radiation
Photon a stream of tiny packets of
energy. (smallest unit of electromagnetic
radiation)
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Emission of energy by atoms
Flame test
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Emission of energy by atoms
Excited states
Only certain energy changes are allowed.
Energy levels are quantized.
(lowest energy level)
Only certain types of photons are produced.
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Bohr model
Electron orbits the nucleus in circles.
Electrons are moving in only allowed energy
levels.
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Wave mechanical model of atom
Electron acts as a wave.
Electron does not orbit the nucleus in
circles. Electrons move randomly however,
there is more chance to find them close to
nucleus.
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n4
n3
Principal energy levels
n2
Energy
n1
ground state (lowest energy level)
Sublevels s p d f
Orbital is a region of space and can hold
maximum 2 electrons
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1S
2S
3S
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3 s, p, d 2 s, p 1 s
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Pauli exclusion principle
Orbital is a region of space and can hold
maximum 2 electrons
magnetic field
paired spins
Two electrons can stay together even with their
opposite charges.
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Sublevels s p d f
p
s
d
f
Px
Py
Pz
2
2226
2222210
222222214
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Level Orbitals Maximum number of electrons
1 1s 2
2 2s, 2p 2 6 8
3 3s, 3p, 3d 2 6 10 18
4 4s, 4p, 4d, 4f 2 6 10 14 32
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Electrons configuration description of the
orbitals that its electrons occupy.
Orbital box diagrams
Electron configuration
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Noble gas notation
1s2 2s1
Li (3)
2s
1s
He 2s1
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Orbital filling order
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s
Hf (72)
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2
4f14 5d2
Xe 6s2 4f14 5d2
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Notice that Cr and Cu are exceptions to the usual
trend. Having half-filled d orbitals adds some
stability.
(You must be able to write the electron
configurations for the first 4 periods.)
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Valence level outermost principle energy level
Valence electrons electrons in highest principal
energy level.
Cl (17)
1s2 2s2 2p6 3s2 3p5
7 valence electrons
1s2 2s2 2p6 3s2 3p6
Ar (18)
8 valence electrons
C (6)
1s2 2s2 2p2
4 valence electrons
8 valence electrons
1s2 2s2 2p6
Ne (10)
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Elements in same column (group) have the same
number of electrons in their valance levels.
Same chemical and physical properties.
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Lewis dot structure
Li
He
Only for main-group element of group of
valance electrons
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Main groups elements
s, p
Transition elements
s, p, d
Inner transition elements
s, p, d, f
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Atomic Size
Size of atom is the size of its outermost
occupied orbital.
d
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Ionization Energy
Li energy ? Li e-
ion
Ionization energy the energy required to remove
the most loosely held electron from an atom in
the gaseous state.
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Ions Electron Configuration

• Ions have electron configurations where the
  neutral atom has lost or gained electrons.
• Oxygen, O, 1s22s22p4 ? Oxide, O2-,
  1s22s22p6
• Sodium, Na, 1s22s22p63s1 ?
• sodium cation, Na, 1s22s22p63s0 1s22s22p6
• Notice both O2- and Na have electron
  configurations identical to the noble gas neon.

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At-home Practice

• What is the correct electron configuration for
  the element phosphorus?
• What is the correct electron configuration for
  the element titanium?
• Which noble gas electron configuration is exactly
  the same as the electron configuration for the
  Ca2 ion?
• Which noble gas electron configuration is exactly
  the same as the electron configuration for the
  Se2- ion?