CHEMISTRY
Chapter 4
Arrangement of Electrons in Atoms
Southern Boone County HS
William Palmer
CHEMISTRY CHAPTER 4
Properties of Light
Electromagnetic Radiation
Wavelike behavior
Visible light
X-Rays
Ultraviolet
Infrared
CHEMISTRY CHAPTER 4
CHEMISTRY CHAPTER 4
Wavelength-Distance between
corresponding parts of a wave
(lambda)
Frequency-Number of waves that pass
a point in a given time (v). Measured
in hertz (HZ)
CHEMISTRY CHAPTER 4
c is speed of light 186,000 miles/sec
frequency X wavelength = speed of light
c=f λ
λ =c/f
f=c/ λ
So what?
As wavelength increases, frequency
decreases
As wavelength decreases, frequency
increases
CHEMISTRY CHAPTER 4
Photoelectric
Effect-emission of
electrons when a
light shines on a
metal.
CHEMISTRY CHAPTER 4
Photoelectric
Effect-emission of
electrons when a
light shines on a
metal.
Light must be of a
high frequency.
Hard to explain
with wave theory of
light.
CHEMISTRY CHAPTER 4
Max Planck (1900)
Objects emit light
in small packets
called quanta.
The Quantum
Theory
CHEMISTRY CHAPTER 4
Quantum of energy
is the smallest
amount of energy
that can be lost or
gained by an atom.
CHEMISTRY CHAPTER 4
Einstein (1905)
Electromagnetic
radiation has a
dual wave-particle
nature!
WOW
CHEMISTRY CHAPTER 4
HYDROGEN ATOM
LINE-EMISSION
SPECTRUM (WOW
THAT IS A MOUTHFUL)
What does it mean?
CHEMISTRY CHAPTER 4
What does it mean?
When a current is
passed through a gas
light is emitted.
In hydrogen gas,
some of the light is
lost-not in spectrum.
This indicates that a
specific amount of
energy from the light
was absorbed by the
atom.
CHEMISTRY CHAPTER 4
Neils Bohr (1913)
Electrons in orbits
Different electrons have
different energy levels (like
rungs on a stepladder)
When in orbit an electron
has constant energy
When electron goes to a
higher energy state it
moves up the ladder
(absorption)
When electron goes to a
lower energy state it moves
down the ladder (emission)
CHEMISTRY CHAPTER 4
Questions 1-5
page 103
Try questions
1-3, page 110
PPT not ready
yet…
CHEMISTRY CHAPTER 4, sec 2
HEISENBURG
UNCERTAINY
PRINCIPLE-It is
hard to tell the
location of an
electron.
Or….in formal
words….
CHEMISTRY CHAPTER 4, sec 2
HEISENBURG
UNCERTAINY
PRINCIPLEIt is impossible to
simultaneously tell
the position and
velocity of an
electron or other
particle. You can
tell one but not the
other.
CHEMISTRY CHAPTER 4, sec 2
QUANTUM
NUMBERS AND
QUANTUM
ORBITALS
Quantum numbers
specify the
properties of
atomic orbitals and
the properties of
electrons in
orbitals.
CHEMISTRY CHAPTER 4, sec 2
PRINCIPAL
QUANTUM
NUMBER (n)
Main energy level
occupied by an
electron.
Positive integers
1, 2, 3, 4 ….
CHEMISTRY CHAPTER 4, sec 2
AS n INCREASES,
THE ELECTRON’S
ENERGY AND
DISTANCE FROM
THE NUCLEUS
INCREASE.
CHEMISTRY CHAPTER 4, sec 2
So, which has
more energyquantum number 4
or quantum
number 6?
Which is closer to
the nucleus of the
atom?
CHEMISTRY CHAPTER 4, sec 2
There are four types of Quantum
Numbers:
1) Main Quantum Number
2) Angular Momentum Quantum Number
3) Magnetic Quantum Number
4)Spin Quantum Number
CHEMISTRY CHAPTER 4, sec 2
Angular
Momentum
Quantum Number
(l)-Indicates the
shape of the orbit.
CHEMISTRY CHAPTER 4, sec 2
S ORBITALS
CHEMISTRY CHAPTER 4, sec 2
P ORBITALS
CHEMISTRY CHAPTER 4, sec 2
D ORBITALS
CHEMISTRY CHAPTER 4, sec 2
F ORBITALS
CHEMISTRY CHAPTER 4, sec 2
Magnetic
Quantum Number
(m)-Indicates the
orientation of the
orbit around the
nucleus.
CHEMISTRY CHAPTER 4, sec 2
Spin Quantum
Number (-1/2,
+1/2)-Indicates the
fundamental spin
state of the
electrons of the
orbit around the
nucleus.
CHEMISTRY CHAPTER 4, sec 2
s = sphere
p = dumbbell
d= complex
dumbbell
f=very complex
shape
CHEMISTRY CHAPTER 4, sec 2
PRINCIPAL
QUANTUM
NUMBER
(n)
SUBLEVELS
IN MAIN
ENERGY
LEVEL
ORBITALS
PER
SUBLEVEL
ORBITALS
PER
ENERGY
LEVEL
ELECTRONS
PER
SUBLEVEL
ELECTRONS
PER MAIN
ENERGY
LEVEL
1
S
1
1
2
2
2
S
1
4
2
8
2
P
3
4
6
8
3
S
1
9
2
18
3
P
3
9
6
18
3
D
5
9
10
18
4
S
1
16
2
32
4
P
3
16
6
32
4
D
5
16
10
32
4
F
7
16
15
32
CHEMISTRY CHAPTER 4, sec 2
Try questions
1-3, page 110
CHEMISTRY CHAPTER 4, sec 3
Electron Configuration
The goal of this section is to figure out
how electrons are arranged in an atom.
There are three rules.
CHEMISTRY CHAPTER 4, sec 3
Electron Configuration
Rule 1: Aufbau Principle-an electron
occupies the lowest energy orbital that
can receive it.
CHEMISTRY CHAPTER 4, sec 3
Electron
Configuration
Rule 2: Pauli
Exclusion PrincipleNo two electrons
can have the same
set of quantum
numbers.
CHEMISTRY CHAPTER 4, sec 3
Electron Configuration
Rule 3: Hund’s Rule –Orbitals of equal
energy are each occupied by one
electron before any orbital is occupied
by a second electron.
CHEMISTRY CHAPTER 4, sec 3
Sample Problem
The electron configuration of Boron is
1s22s22p1.
How many electrons are present in an atom
of Boron? (2+2+1 = 5 electrons)
What is the atomic number of Boron?
(protons = electrons so with 5 electrons
there are 5 protons so Atomic No. of Boron =
5)
CHEMISTRY CHAPTER 4, sec 3
Sample Problem
The electron configuration of Boron is
1s22s22p1.
Write the orbital notation for Boron.
↑↓
↑↓ ↑
1s
2s 2p
CHEMISTRY CHAPTER 4, sec 3
Practice Problem
The electron configuration of Nitrogen
is 1s22s22p3.
How many electrons are in Nitrogen?
2. What is the atomic number of
Nitrogen?
3. Write the orbital notation for Nitrogen.
1.
CHEMISTRY CHAPTER 4, sec 3
Practice Problem
The electron configuration of Fluorine
is 1s22s22p5.
How many electrons are in Fluorine?
2. What is the atomic number of
Fluorine?
3. Write the orbital notation for Fluorine.
1.
CHEMISTRY CHAPTER 4, sec 3
Second Period Elements
See chart page 116
Third Period Elements
See chart page 117
Fourth Period Elements
See chart on page 118
FIGURE 19, PAGE 116, IS WHERE YOU
LEARN HOW THE ELECTRONS FILL THE
ORBITALS
CHEMISTRY CHAPTER 4, sec 3
Second Period Elements
See chart page 116
Third Period Elements
See chart page 117
Fourth Period Elements
See chart on page 118
FIGURE 19, PAGE 116, IS WHERE YOU
LEARN HOW THE ELECTRONS FILL THE
ORBITALS
CHEMISTRY CHAPTER 4, sec 3
FIGURE 19, PAGE 116, IS WHERE YOU
LEARN HOW THE ELECTRONS FILL THE
ORBITALS
CHEMISTRY CHAPTER 4, sec 3
Sample Problem
Write the electron configuration for a
Rubidium atom. (Atomic Number = 37)
1s22s22p63s23p63d104s24p65s1
Write the Noble-gas configuration for
Rubidium.
[Kr] 5s1
CHEMISTRY CHAPTER 4, sec 3
Sample Problem
Identify the elements in the second,
third, and fourth periods that have the
same number of highest energy level
electrons as Rubidium.
Rubidium has one electron in its highest
energy level…(the 5th). Other elements that
have one electron in their highest energy
level are: Li, Na, and K.
CHEMISTRY CHAPTER 4, sec 3
Practice Problem
Write the electron configuration and
Noble gas notation for a Barium atom.
(Atomic Number = 56)
1s22s22p63s23p63d104s24p64d105s25p66s2
CHEMISTRY CHAPTER 4, sec 3
Practice Problem
Write the electron configuration and
Noble gas notation for a Barium atom.
(Atomic Number = 56)
1s22s2p63s23p63d104s24p64d105s25p66s2
[Xe] 6s2
CHEMISTRY CHAPTER 4, sec 3
Practice Problem
Write the Noble gas notation for a Gold
atom. (Atomic Number = 79)
1s22s2p63s23p63d104s24p64d105s25p66s2
[Xe] 4f145d106p1
CHEMISTRY CHAPTER 4, sec 3
Practice Problem
Identify the elements in the sixth period
that have one unpaired electron in their
6s level.
Au, Cs, Pt
CHEMISTRY CHAPTER 4, sec 3
Practice Problem
Let’s try the work sheet on Chap 4, sec
3.