South Pasadena • Chemistry
Name
Period
Date
9 · Atomic Structure
ELECTRON
CONFIGURATION WORKSHEET
1. For each of the following elements, (a) find the total number of electrons in the neutral atom, (b) fill in the orbital
diagram, and (c) write the electron configuration (long form).
Element
Carbon
Phosphorous
Oxygen
Fluorine
Silicon
Boron
6
15
8
9
14
5
–
# of e s
3s
Orbital
Diagram
Electron
Config.
3p
3s
2p
3p
3s
3p
3s
2p
2p
3p
3s
2p
3p
3s
2p
2p
2s
2s
2s
2s
2s
2s
1s
1s
1s
1s
1s
1s
1s2 2s2 2p2
1s2 2s2 2p6 3s2
3p3
1s2 2s2 2p4
1s2 2s2 2p5
2. Consider the element iron.
(a) How many electrons are in the neutral atom?
26
(b) Fill in the orbital diagram to the right.
(c) Write the long form electron configuration for iron.
1s2 2s2 2p6 3s2 3p6 4s2 3d6
1s2 2s2 2p6 3s2
3p2
4s
3s
4p
3d
3p
2p
(d) The valence electrons are those on the highest energy level. These are
the electrons we would “bump” into first. Place a box around the
valence electrons in (c).
How many valence electrons are in iron?
2s
1s
2
3. For each of the following, write the long form and short form electron configurations.
(a) Ar (# of electrons: 18)
3s
Long: 1s2 2s2 2p6 3s2 3p6
3p
2p
2s
Short: [Ne] 3s2 3p6
1s
(b)
Mg (# of electrons: 12)
3s
Long: 1s2 2s2 2p6 3s2
3p
2p
2s
Short: [Ne] 3s2
1s
(c)
N (# of electrons: 7)
3p
3s
Long: 1s2 2s2 2p3
3p
2p
2s
Short: [He] 2s2 2p3
1s
1s2 2s2 2p1
(d)
Li (# of electrons: 3)
3s
Long: 1s2 2s1
3p
2p
2s
Short: [He] 2s1
1s
(e)
Cl (# of electrons: 17)
3s
Long: 1s2 2s2 2p6 3s2 3p5
3p
2p
2s
Short: [Ne] 3s2 3p5
1s
(f)
Zn (# of electrons: 30)
4s
Long: 1s2 2s2 2p6 3s2 3p6 4s2 3d10
3s
Short: [Ar] 4s2 3d10
4p
3d
3p
2p
2s
1s
(g)
Zn2+
(# of electrons: 30–2 = 28)
4s
Long: 1s2 2s2 2p6 3s2 3p6 3d10
3s
Short: [Ar] 3d10
4p
3d
3p
2p
2s
When you form a cation, you remove electrons from the highest energy
level.
1s
4. For each of the elements in the oxygen family, (a) write the number of electrons in the neutral atom, (b) fill in the
orbital diagram, (c) write the short form electron configuration, (d) circle the valence electrons in the electron
4p
configuration,
and (e) 3d
write the number of valence electrons.
4s
Element
# of e–s
3s
Oxygen
3p
Sulfur
8
2p
Selenium
16
3p
Tellurium
34
4s
4p
3d
52
2s
3s
1s
2s
3s
1s
2s
3s
1s
2s
2p
5s
3p
4s
2p
Orbital
Diagram
5p
4d
4p
3d
3p
2p
1s
Electron
Config.
[He] 2s2 2p4
[Ne] 3s2 3p4
[Ar] 4s2 3d10 4p4
[Kr] 5s2 4d10 5p4
Val e–s
6
6
6
6
5. How many valence electrons are in these elements?
Per
1
2
13
14
15
16
17
1
H
1
2
Li
1
Be
2
B
3
C
4
N
5
O
6
F
3
Na
1
Mg
2
Al
3
Si
4
P
5
S
6
4
K
1
Ca
2
Ga
3
Ge
4
As
5
Se
5
Rb
1
Sr
2
In
3
Sn
4
Sb
5
6
Cs
1
Ba
2
Tl
3
Pb
4
Bi
5
7
Fr
1
Ra
2
18
He
2
7
Ne
8
Cl
7
Ar
8
6
Br
7
Kr
8
Te
6
I
7
Xe
8
Po
6
At
7
Rn
8
Using complete sentences, describe the pattern for numbers of valence electrons.
As you move from left to right across the periodic table, the number of valence electrons increases.
6. You can tell from the periodic table which orbital is filled last for each element. For each block, write the orbital
that is filled by the elements in that block.
1s
1s
2s
2p
3s
3p
4s
3d
4p
5s
4d
5p
6s
5d
6p
7s
6d
7p
4f
5f
7. Using the periodic table, write the short form electron configuration for the following elements.
(a) As
[Ar] 4s2 3d10 4p3
(b) W
[Xe] 6s2 4f14 5d4
(c) Li
[He] 2s1
(d) U
[Rn] 7s2 5f4
(e) O
[He] 2s2 2p4
(f) Rn
[Xe] 6s2 4f14 5d10 6p6
(g) V
[Ar] 4s2 3d3