Leader: Sara
Course: Chem177D
Instructor: Bonaccorsi
Supplemental Instruction
Date: 10/23/13
Iowa State University
1) Write the complete and condensed electron configuration of Mo. (hint: it behaves
just like Cr)
1s22s22p63s23p64s23d104p65s14d5
[Kr] 5s14d5
2) How many valence core and pair electrons does Se and Se2- have (write the
electron configurations)
Se: 1s22s22p63s23p64s23d104p4 core:28
valence: 6 unpaired: 2
22
2
6
2
6
2
10
6
Se : 1s 2s 2p 3s 3p 4s 3d 4p core:28
valence: 8 unpaired:0
3) How many total orbitals are in an atoms that had a full 3p subshell? How many
electrons?
Orbitals = n2 = 32 = 9
Electrons = 2n2 = 18
4) What is isoelectronic?
Elements/ ions with the same number of electrons
Worksheet 7A:
Periodic Table
5) Effective Nuclear Charge: the net positive charge experienced by an electron in
a many-electron atom. What is the equation?
Zeff = Z – S
Z = atoms number (# of protons or electrons)
S = Shielding/Screening electrons (core electrons)
6) Which element had the highest and which has the lowest Neff:
Na
Al
Mg
Si
Cl
Ar
S
Lowest: Na
Highest: Ar
7) Show the Zeff trend on the periodic table:
Smaller Z eff
Larger Z eff
8) What atom has the LARGEST atomic radius?
Francium
9) What atom has the SMALLEST atomic radius?
Helium
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10) Which of the following molecules would you expect to be Largest?
a. Br2
Cl2
Br2
b. NaCl
KCl
KBr
NaBr
KBr
11) Show the atomic radius trend on the periodic table:
Smallest radius
Largest radius
12) If the charge of an atom changes, does the radius of the atom change?
Yes
Cations are smaller, anions are larger
13) Rank the following in order of size smallest to largest:
a. Ra
Ca
P
Ga
Fr
O
O
P
Ga
Ca
Ra
Fr
14) Which is larger?
a. Mg
or
Mg2+
b. I
or
I-
c. K
or
K+
d. Se
or
Se2-
e. Cl-
or
Br-
f. F-
or
Ne
g. N3-
or
P3-
15) Put the following in order of increasing radius:
BrSe2- Sr2+ Kr
RbSe2- BrKr
Rb- Sr2+