Midterm 2
Given that in an NO heteronuclear diatomic the 2p>2p draw the MO diagram. Is it paramagnetic or
diamagnetic? What is the bond order? Would adding an electron add or subtract from the bond order?
(Hints: remember to label both the atomic and molecular orbitals including subscripts. Include all
electrons in both atomic and molecular orbitals.)
Para/dia magnetic? _para______
Bond Order____2.5___
Add or subtract?___subtract_____
A) Draw the line structure of CH3CH(OH)CHCH2.
B) What is the empirical formula of the structures shown below.
C11H12N2O3
For each formula, draw the lewis structure:
A) PCl3
B) O3
C) BrF5
Lewis Structures:
For each of the following lewis structures, decide if it is correct. If it is not, fix it. If there is
resonance, only draw one structure.
a)
b)
c)
d)
a) Incorrect use the two radical electrons to form a bond
b) incorrect, you need one oxygen on each nitrogen to have a double bond.
c) Incorrect put double bond between CO not CH leaving two lone pairs on O
d) incorrect triple bond between CN leaving one lone pair on N
Why do electron affinity and electronegativity share the same trend? Why does electron affinity have pblock exceptions but electronegativity does not even though they share the same trend (be specific and
give one example of an exception in your answer)?
In both cases they are based on the effective nuclear charge. Electron affinity is not only based on
effective nuclear charge but also on stable electron configurations. (they may also say something like
thing, stable half shells change electron affinity but not electronegativity).
Many Correct Examples
If given two resonance structures of equal stability. How does this affect bond order? How does this
affect the location of formal charges?
Sigma bonding electrons are shared only amongst the atoms in the specific bond. Pi bonds are
delocalized to be an average of resonance structures. The bond order is an average of all the lewis
structures The formal charge is an average of all the lewis structures.
Which has more covalent character BeCl2 or AgF? Why? Be specific. Describe the behavior of both
species in the molecule and how each contributes to the ionic or covalent character.
AgI. “difference in electronegativity”: if this is all they have, however if they answer the other two parts
correctly they don’t actually need this. The more polarizing power the cation has the more covalent
character. The more polarizability the anion has the more covalent character
Rank C, N and O in terms of increasing electron affinity. Explain the order.
N, C, O: effective nuclear charge causes it to increase as you go right on the periodic table.
However C and N are reversed because of the stability caused by the half filled p orbital in
nitrogen.
Quantum numbers: State whether each set of quantum numbers is allowed. If they are, give the missing
quantum numbers, state how many orbitals and how many electrons are present with those quantum
numbers. (book/sapling/class/reviewsheet)
A) a) n=6
i) ml=?
l=1 and 3
ii) number of orbitals?
±3, ±2, ±1, 0
10
b) n=4
i) l=?
ml=-1, 0, 1
ii)number of orbitals?
3, 2, 1, 0
10
c) n=5
iii) Number of electrons?
20
iii) Number of electrons?
20
l=4 ms= +1/2
i) ml=?
ii) number of orbitals?
±4, ±3, ±2, ±1, 0,
9
iii) Number of electrons?
9
Quantum Numbers
Which set of quantum numbers, n, l correspond to one of the highest energy electrons in the ground
state of Cobalt?
N=3, l=2
How many orbitals in a single atom may have the quantum numbers: n=5 or 4, l=3, ms=+1/2
14
How many electrons in a single atom may have the quantum numbers: n=5 or 4, l=3, ms=+1/2
14
Electron Configurations
Which is the ground-state electron configuration of In+?
A) [Kr]4d75s25p3
D) [Kr]4d105s2
B) [Kr]4d85s15p3
E) [Kr]4d105s15p1
C) [Kr]4d55s15p6
D
Write the ground-state electron configuration of a neutral sulfur atom.
[Ne]3s23p4
What is the electron configuration of S2-?
[Ne]3s23p6
Give the electron configuration for neutral copper. Use the noble gas short hand notation.
[Ar]4s13d10
Give the electron configuration of the +1 ion of the element given in the previous problem. Use the
noble gas short hand notation.
[Ar]3d10
Is the following electron configuration of phosphorous a ground state or excited state configuration?
3s13p4.
Excited
If a +3 ion is made from antimony, which orbital(s) are the electrons removed from? (be sure to include
the energy level and subshell)
5p
If a +4 ion is made from lead, which orbital(s) are the electrons removed from? (be sure to include the
energy level and subshell)
6p and 6s
Orbitals
Which of the following orbital(s) is/are most shielded (assume all listed orbitals are filled): 1s, 3s, 4d, 5s
4d
How many nodes are present in a 4s orbital?
3
Lewis Structures
How many lone pairs are found on the central atom in the Lewis structure of XeF4
2
How many double bonds are present in the “best” resonance structure of the sulfate ion?
2
MO Theory
What is the bond order of N22- ? (hint: use MO theory).
2
Which of the following has the strongest bond? (hint: use MO theory).
A) N2
B) O22- C) N22+
D) N22-
E) impossible to tell
A
If you add an electron to an anti- bonding orbital does it increase or decrease the bond order?
decrease
Periodic Trends
If the first ionization energy of copper is 1958 kJ·mol-1, the second ionization energy is likely to be
________________(greater or less) than 1958 kJ·mol-1.
greater
Which of the following has the largest atomic radius ? F, Na, Li, He, or N
Na
Put the following in order of INCREASING ionization energy. C, N, O.
C,O,N
Which of the following atoms is most polarizable? S, Se or Te.
Te
Order the following in terms of INCREASING atomic radius. P, N, As.
N, P, As
Order the following in terms of INCREASING electron affinity. Ti, Cr, V
Ti, V, Cr
Order the following in terms of INCREASING ionization energy. Si, P, S
Si, S, P
Combined all topics in valence bond theory.
Use the Lewis structure below to answer the following questions.
The bond length for a single Cl-O bond is 170 pm, the bond length for a double Cl-O bond is 144pm.
What would you expect the bond length of the Cl-O bond in chlorite to be?
157pm
What is the formal charge on the oxygen of the chlorite atom?
-0.5
Would you expect to have the same experimental bond order on both ions?
no
Given the structures below, answer the following questions: (Note: no lone pairs are shown, you may fill
if necessary to answer the questions)
What is the bond order of the sulfate SO bond?
1.5
Which ion has the longest bonds?
phosphate
What is the charge on the oxygen of the phosphate?
-3/4