Center for Academic Services & Advising
November 9, 2015
Chemistry I
CSI Worksheet 9
1. Determine whether each transition in the Hydrogen atom corresponds to absorption or emission of energy
a. n = 3 → n = 1
emission: electron is moving to a lower energy level
b. n = 2 → n = 4
absorption: electron is moving to a higher energy level
c. n = 4 → n = 3
emission: electron is moving to a lower energy level
2. Write the full electron configuration for each element
a. C
1s22s22p2
b. P
1s22s22p63s23p3
c. Ar
1s22s22p63s23p6
d. Na
1s22s22p63s1
3. Determine the element corresponding to each electron configuration
a. [Ar] 4s23d104p6
Kr
b. [Ar] 4s23d2
Ti
c. [Kr] 5s24d105p2
Sn
d. [Kr]5s2
Sr
4. Determine the number of valence electrons in each element. Which elements do you expect to lose
electrons in chemical reactions? Which do you expect to gain electrons?
a. Al
3 because in column 3A; will lose 3 electrons to have the same configuration as [Ne]
b. Sn
4 because in column 4A; will either lose 4 electrons to have the configuration of [Kr] or two to
have the configuration of Cd
c. Br
7 because in column 7A; will gain one electron to have the configuration of [Kr]
d. Se
6 because in column 6A; will gain two electrons to have the configuration of [Kr]
5. Arrange the following atoms according to decreasing effective nuclear charge experienced by their
valence electrons: S, Mg, Al, Si
S = [Ne] 3s23p4
Mg = [Ne] 3s2
Al = [Ne] 3s23p1
Si = [Ne] 3s23p2
COLORADO SCHOOL OF MINES
Frances I Core Supplemental Instruction Facilitator | Chemistry II
Center for Academic Services & Advising
All of them have the same number of core electrons to contribute to shielding so nuclear charge will be
due to the number of protons
S = 16
Mg = 12
Al=13
Si=14
Oder: S>Si>Al>Mg
6. Write the electron configuration for each ion:
a. ClCl = [Ne] 3s23p5
Cl-= [Ne] 3s23p6
b. P3P =[Ne]3s23p3
P3- = [Ne] 3s23p6
c. K+
K = [Ar] 4s1
K+= [Ar]
d. Mo3+
Mo = [Kr]5s14d5
Mo3+= [Kr] 5s04d3 OR
[Kr] 4d3
e. V3+
V = [Ar]4s23d3
V3+= [Ar] 4s03d2
OR
[Ar]3d2
7. Arrange the following elements in order of decreasing first ionization energy: Cl, S, Sn, Pb
Ionization energy increases moving across the periodic table to the right and increases moving up each
column
Cl>S>Sn>Pb
8. Choose the element with the more negative (more exothermic) electron affinity from each pair:
a. Mg or S
S
b. K or Cs
K
c. Si or P
Si
d. Ga or Br
Br
9. Arrange the following elements in order of decreasing metallic character: Sr, N, Si, P, Ga, Al
Metallic character decreases moving left to right across the periodic table and decreases moving up a
column
Sr>Ga>Al>Si>P>N
10. Write a balanced chemical equation for the reaction of chlorine gas with fluorine gas
COLORADO SCHOOL OF MINES
Frances I Core Supplemental Instruction Facilitator | Chemistry II