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
Number that specifies the properties of the
atomic orbitals
Tells us the distance from the nucleus and
the shape of the orbital



Main level or shell
These are the Bohr energy levels
n = 1, n = 2, n = 3
As n increases, the distance from the nucleus
increases
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
Each main level is divided into sublevels
Four types of sublevels
s
p
d
f
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
Each sublevel is made of orbitals
Every orbital can hold 2 electrons




s – 1 orbital – 2 electrons
p – 3 orbitals – 6 electrons
d – 5 orbitals – 10 electrons
f – 7 orbitals – 14 electrons

One spherical
shaped orbital


Three dumbbell shaped
One dumbbell in each axis
Main Level
Sublevels
Number of
Sublevels
Electrons in
sublevels
Total
Electrons in
Main Level
1
s
1
2
2
2
s
p
1
3
2
6
8
3
s
p
d
1
3
5
2
6
10
4
s
p
d
f
1
3
5
7
2
6
10
14
18
32
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
Arrangement of electrons in an atom
Aufbau Principle – electrons fill into an atom
starting with the lowest energy levels


Way which the electrons rotate on their axis
Pauli Exclusion Principle – in order for two
electrons to occupy the same orbital, they
must have opposite spin
Hund’s Rule – electrons occupy orbitals
singly first before doubling up

Write the configuration for each of the below
C
S
Br
Na
Cl
Kr



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Electrons in the last main energy level
These are the electrons farthest out on the
atom
These will interact with other atoms
These are the electrons involved in chemical
reactions
There are a maximum of 8 valence electrons


Write configuration and count electrons in
last main energy level
Examples: Find valence electrons for
C
Na
P
Fe
Ar

Atoms will give up, accept, or share electrons
in order to achieve a filled valence shell (8
valence electrons)



Metals become more reactive (more metallic
in character) as you go down a group
Most metallic elements bottom left corner of
the periodic table
Least metallic, top right corner





Energy required to remove the most loosely
held electron from an atom
The greater the ionization energy, the more
strongly the atom holds onto its electrons
M + energy → M+ + e
Ionization energy increases as moving
across a period
Ionization energy decreases as moving
down a group



Half of the distance between two adjacent
nuclei
Radius decreases across a period (atoms hold
the electrons tightly in)
Radius increases down a group