Chemistry
Ch. 5 Notes #2
Electrons in Atoms
Energy of Atoms

Energy Levels
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Where electrons are found
Principal Energy Levels (p.e.l.)
 7 “orbits” – each has one or more sublevels in it
The number of sublevels in any p.e.l. is the same
as its number “n”.
 Ex. P.e.l. 1 has 1……. p.e.l. 2 has 2, etc
p.e.l’s are represented by numbers 1-7
Energy of Atoms

Sublevels

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Designated by numbers and letters
The # represents the p.e.l
The letter refers to the sublevel

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First 4 sublevels = s, p, d, f
Each electron has specific energy
Each p.e.l. has as many sublevels as its number “n”
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Energy level 1 = 1 sublevel = 1s
Energy level 2 = 2 sublevels = 2s and 2p
Energy level 3 = 3 sublevels = 3s, 3p, and 3d
Energy of Atoms
Principal energy
level
Sublevels
1
1s
2
2s
2p
3
3s
3p
3d
4
4s
4p
4d
4f
5
5s
5p
5d
5f
6
6s
6p
6d
6f
Shapes of Sublevels

All s orbitals are
spherical.
 Each new p.e.l. s
sublevel is bigger
than the last
 2s is larger than 1s
Shapes of Sublevels

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All p orbitals
are dumb-bell
shaped
px, pz, and py
each have a
different
orientation
Energy of Atoms


The d and f sublevels do not all have the same
shapes…..
Inside the sublevels = orbitals

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Each orbital holds 2 electrons
The 2 electrons have opposite “spins”

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Compared to earth’s rotation on its axis
With each new sublevel there are 2 more orbitals
available
Energy of Atoms
p.e.l
n
Number of Orbitals Available
s
p
d
f
#
Max #
orbital of es
2
2n
2
n
1
1
-
-
-
1
2
2
1
3
-
-
4
8
3
1
3
5
-
9
18
4
1
3
5
7
16
32
Sublevels

Orbitals are drawn out as boxes

The 3 p orbitals are referenced as px, py, pz
Each orbital holds 2 electrons
In Mult. Orbital sublevels, each orbital has to have 1
e- of the same spin before they double up (by gaining
a second e- of the opposite spin)
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Sublevels
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Electrons always fill from lowest energy levels
to highest energy levels
No electron can remain in a particular orbital if
there is a vacant orbital at lower energy
Once you get to the 3rd p.e.l. there is overlap in
energy amongst the levels
If an electron jumps to a higher level (an
“excited” state) it emits frequencies of light
(emission spectra) to go back to “ground state”
Sublevels
Electron Configurations
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The arrangement of electrons among the
various orbitals of an atom is called the
electron configuration
It is written using a notation that tells us the
p.e.l. and sublevels that are filled.
Every element has a different electron
configuration
Electron Configurations
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Order that
sublevels fill….
1s, 2s, 2p, 3s, 3p,
4s, 3d, 4p, 5s, 4d,
5p, 6s, 4f, 5d, 6p,
7s, 5f, 6d, 7p
Electron Configurations
Element Atomic
#
H
1
He
2
Li
3
Be
4
Orbital Diagram
Electron
Configuration
Electron Configurations
Element
Atomic
#
B
5
C
6
N
7
O
8
F
9
Ne
10
Na
11
Mg
12
Orbital Diagram
Electron
Configuration