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CH301 Fall 2009 Worksheet 3
Answer Key on Electronic Configuations and Periodic Table Trends
1. Write the electron configuration of gallium (Ga) in long notation and in short notation.
1s
2
2s
2
2p
6
3s
2
3p
6
4s
2
3d
10
4p
1
[Ar] 4s
2
3d
10
4p
1
2. Write the electron configuration of a divalent vanadium cation (V
2+
) in long and in short
notation.
1s
2
2s
2
2p
6
3s
2
3p
6
4s
2
3d
1
[Ar] 4s
2
3d
1
3. Write the electron configuration of a monovalent iodine anion (I

) in long and in short
notation.
1s
2
2s
2
2p
6
3s
2
3p
6
4s
2
3d
10
4p
6
5s
2
4d
10
5p
6
[Kr] 5s
2
4d
10
5p
6
4. State in your own words the Pauli exclusion principle. Which of the quantum numbers is it
most concerned with?
In a given atom, all of the electrons must be described by a unique set of four quantum
numbers (n, l, m
l
and m
s
). It is most concerned with m
s
, since for any value of n, l and m
l
,
m
s
must be different, ensuring that the electrons have opposite spins. So, for our purposes,
the Pauli exclusion principle states that any two electrons in the same orbital must have
opposite spins.
5. Which ground state element corresponds to the following electron configurations?
a. [Rn] 5f
14
6d
3
7s
2
Dubnium (Db)
b. [Ne] 3s
2
3p
4
Sulfur (S)
c. [Xe] 4f
14
5d
6
6s
2
Osmium (Os)
d. [Xe] 4f
14
5d
10
6s
1
Gold (Au)
6. In your own words, what does Hund's rule state?
Every orbital in a subshell must have one electron in it before any orbital can have a pair of
electrons in it. In other words, we half fill all orbitals before completely filling any of them.
(For the record, Hund had 3 rules, but we're only concerned with the 1st one.)
7.In which region of the periodic table do we find most of the exceptions to Aufbau for
neutral, ground state elements? What about cations (positively charged ionic species)?
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This note was uploaded on 06/14/2011 for the course MATH 305G taught by Professor Cathy during the Spring '11 term at University of Texas at Austin.
 Spring '11
 Cathy

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