CHAPTER 11 – MODERN ATOMIC THEORY
ELECTROMAGNETIC RADIATION – Forms of energy that travel in waves at
the speed of light
SPEED OF LIGHT (c) – 3.00  108 m/s
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AMPLITUDE (A) – The maximum disturbance in the medium during one
wave cycle
WAVELENGTH (λ) – The distance between two sequential crests
FREQUENCY (ν) – The number of complete cycles per unit time
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EM Radiation also behaves as a stream of particles when interacting with
matter
PHOTON – A particle of EM radiation, acting as a packet of energy
Photons of different types of EM Radiation have different energies
Radiowaves – Lowest energy photons
Gamma Rays – Highest energy photons
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ENERGY STATES OF ATOMS
GROUND STATE – The lowest energy state of an atom
EXCITED STATE – An atom with excess energy
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Atoms in the ground state absorb photons of EM radiation to jump to
excited states
Atoms in excited states release photons of EM radiation to return to the
ground state
Hydrogen atoms release three
photons in the visible spectrum
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1913 NIELS BOHR
Proposed that electrons orbit the nucleus in specific circular
orbits
Verizon Amphitheatre
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QUANTUM THEORY – Any theory that predicts that a property is
restricted to specific values
The energy of an electron is quantized because the electron can only be
specific distances from the nucleus
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ENERGY LEVEL – The position of an electron in an atom, determined by
its distance from the nucleus
Electrons absorb energy to jump to higher energy levels
Electrons release energy to drop to lower energy levels
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However, the Bohr model only worked for atoms or ions with 1 electron
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1926 ERWIN SCHRÖDINGER
Proposed a model of the hydrogen atom in which the electron
is mathematically treated as a wave, not a particle
ORBITAL - A highly probable volume of space in an atom where an electron
can be found
Orbit
Orbital
A maximum of 2 electrons can exist in an orbital, but they must be spinning
in opposite directions
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Orbitals in atoms are organized by
1) Energy Level
The distance the orbital is from the nucleus
1st Energy Level
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2nd Energy Level
3rd Energy Level
etc.
Orbitals in Energy Levels are organized by
2) Sublevel
The shape of the orbital
s orbital
spherical
p orbital
dumbbell
d orbital
4-leaf clover
f orbital
8-leaf clover
s orbitals
1 per EL
p orbitals
3 per EL
d orbitals
5 per EL
f orbitals
7 per EL
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etc.
Energy
Level
Sublevels
Number of
Orbitals
Number of
Electrons
1
2
3
1 (s)
2 (s, p)
3 (s, p, d)
1 (1)
4 (1+3)
9 (1+3+5)
2
8
18
4
4 (s, p, d, f)
16 (1+3+5+7)
32
n
n
n2
2n2
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FIRST ENERGY LEVEL
1 “s” orbital
 2 electrons fit in the 1st EL
An orbital is named by stating its energy level and its sublevel
1s orbital
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SECOND ENERGY LEVEL
1 “s” orbital and 3 “p” orbitals
 8 electrons fit in the 2nd EL
2s orbital
2p orbital or 2px orbital
2p orbital or 2py orbital
2p orbital or 2pz orbital
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THIRD ENERGY LEVEL
1 “s” orbital, 3 “p” orbitals, and 5 “d” orbitals
 18 electrons fit in the 3rd EL
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3d orbital
3s orbital
3d orbital
3p orbital
3d orbital
3p orbital
3d orbital
3p orbital
3d orbital
FOURTH ENERGY LEVEL
1 “s” orbital, 3 “p” orbitals, 5 “d” orbitals, and 7 “f” orbitals
 32 electrons fit in the 4th EL
1 “4s”, 3 “4p”, 5 “4d” orbitals
4f orbital
4f orbital
4f orbital
4f orbital
4f orbital
4f orbital
4f orbital
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ELECTRON ARRANGEMENTS
Orbital Notation
H
1s
↑
___
He
1s
↑↓
___
ELECTRON PAIR – 2 electrons of opposite spin in the same orbital
Electron Configuration Notation
1s1
1s2
Electron Dot Notation
H.
He :
VALENCE ELECTRONS – The electrons in an atom’s highest occupied
energy level
Electron Dot Notation only shows valence electrons
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Orbital Notation
1s
↑↓
Li
___
Be
___
B
C
N
↑↓
↑↓
___
↑↓
___
↑↓
___
Electron
Dot Notation
2p
___
↑
1s2 2s1
Li .
↑↓
1s2 2s2
Be :
___
↑↓
___
↑↓
___
↑↓
___
.
↑
___ ___ ___
↑
↑
___ ___ ___
↑
↑
1s2 2s22p1
B:
.
↑
___ ___ ___
O
___
___
↑↓
↑↓ ↑
F
___
___
___ ___ ___
Ne
___
___
___ ___ ___
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↑↓
2s
Electron
Conf. Notation
↑
___ ___ ___
1s2 2s22p2
.
C:
.
1s2 2s22p3
.
N. :
..
1s2 2s22p4
.
O. :
Picture of a neon atom:
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In a sublevel of multiple orbitals, electrons remain unpaired as long as
possible to minimize repulsion
36
1st Series:
H
2nd Series:
Li Be B
4
7
X 21
O
F
58
He
C
N
Ne
OCTET – An electron arrangement in which the s and p sublevels are filled
in an energy level of an atom
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3rd Series:
Electron Configuration
Notation
Electron Dot
Notation
Na
1s2 2s22p63s1
Na .
Mg
1s22s22p63s2
Mg :
Al
1s2 2s22p63s23p1
Si
1s2 2s22p63s23p2
.
Al
:
.
.
Si :
…
..
Ar
1s2 2s22p63s23p6
K
1s2 2s22p63s23p64s1
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:
Ar
..
K.
:
SUBLEVEL FILLING PATTERN
The position of each element tells the sublevel of its final electron
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SUBLEVEL FILLING PATTERN
Potassium
1s22s22p63s23p64s1
[Ar]4s1
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SUBLEVEL FILLING PATTERN
Arsenic
1s22s22p63s23p64s23d104p3
[Ar]4s23d104p3
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SUBLEVEL FILLING PATTERN
Iodine
1s22s22p63s23p64s23d104p65s24d105p5
[Kr]5s24d105p5
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SUBLEVEL FILLING PATTERN
Platinum
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VALENCE (OUTER SHELL) ELECTRONS
..
.
K.
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.
As
.
:
.
I
..
:
Pt
PERIODIC TRENDS
1)
CHEMICAL ACTIVITY
Depends upon whether the element is a metal or nonmetal
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METALS
Alkali metals are the most active, with activity decreasing right to
the Noble Metals
Al, Zn are active, with activity decreasing down and to the right
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NONMETALS
F is the most active, with activity decreasing down and to the left
H is active, the Noble Gases are inert
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2)
ATOMIC SIZE
Group – The atom sizes increase moving down a column
the more energy levels an atom has the larger it will be
Period – The atom sizes decrease moving to the right
with the same number of energy levels, the more protons an atom has
the smaller it will be
Atom with the largest atomic radius ?
Atom with the smallest atomic radius?
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3)
IONIZATION ENERGY
IONIZATION ENERGY – The energy need to remove an electron from
an atom
X → X+ + eGroup – The ionization energy decreases moving down a column
the more energy levels the atom has, the further the valence electrons
are from the nucleus
Period – The ionization energy increases moving to the right
with the same number of energy levels, the more protons the atom has
the stronger the attraction to the valence electrons
Atom with the largest IE?
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Atom with the smallest IE?
Metals have low IE’s and nonmetals have high IE’s
 Metals easily lose electrons, nonmetals don’t
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4)
ELECTRON AFFINITY
ELECTRON AFFINITY – The energy released when an electron is
removed from an atom
X + e- → XGroup – The electron affinity decreases moving down a column
the more energy levels the atom has, the further a free electron is from
the nucleus
Period – The electron affinity increases moving to the right
with the same number of energy levels, the more protons the atom has
the stronger the attraction to a free electron
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Metals have low EA’s and nonmetals have high EA’s
 Nonmetals easily gain electrons, metals and Noble Gases don’t
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