Created by Carol J Breaux, College of the Ozarks, cbreaux@cofo.edu and posted on
VIPEr (www.ionicviper.org) on July 16, 2012, Copyright Carol J. Breaux, 2012. This work is licensed under
the Creative Commons Non-Commercial Share Alike License. To view a copy of this license visit
http://creativecommons.org/about/license/
Calculate the number of valence
electrons available in an ion of CO32-.
18
20
22
24
26
Carbon has 4 valence electrons, each oxygen has 6 valence electrons,
and there are two for the charge.
Which of the following species is
NOT isoelectronic with the others?
SiF2
CO32-
NO3SO3
BF3
All have 24 valence electrons, except SiF4 which has 18 (Si has 4 and each
F has 7)
How many sigma and how many pi bonds in a
molecule of HCN?
4 sigma, 0 pi
3 sigma, 0 pi
2 sigma, 2 pi
3 sigma, 1 pi
2 sigma, 1 pi
The CH bond is a sigma bond, one of the bonds from the CN triple bond is
a sigma bond and the other two are pi bonds
What type of hybridization would exist
around the central atom in NCl3?
sp3
sp2
sp
sp3d
s
There are three bonding pairs and one nonbonding pair on the nitrogen
which will hybridize into 4 sp3 hybrid orbitals
The electron geometry of nitrogen
trichloride is
linear
Trigonal pyramid
Trigonal planar
bent
tetrahedral
Electron geometry includes the lone pair. There are four pairs of electrons
around the central nitrogen giving a tetrahedral electron geometry
The expanded shell around the chlorine
in ClF3 contains how many electrons?
8
10
11
12
14
There are 28 valence electrons in this compound. The central Cl atom
will have three bonding pairs of electrons to the fluorines and two lone
pairs of electrons to accommodate all of the valence electrons
Increasing numbers of lone pairs on a
central atom cause bond angles to
decrease.
Electron pairs will repulse each other and will go as far apart from each
other as they can. Lone pair-bonding pair repulsion is greater than
bonding pair-bonding pair repulsion.
The molecular geometry of PCl6using VSEPR theory is
linear
octahedral
tetrahedral
Trigonal pyramidal
Trigonal planar
There are 48 valence electrons that can be accommodated by a central
P atom and 6 Cl atoms bonded octahedrally around the central atom. There
are no lone pairs around the central P.
For which of the following compounds
will the electron geometry and
molecular geometry be the same?
NH3
H2O
SF4
CO2
XeF2
The electron geometry and the molecular geometry will be the same
For CO2 because it is the only one that does not have any lone pairs on
the central atom
A compound of type AX4E2 will have
which molecular geometry?
tetrahedral
Square planar
Trigonal pyramid
Trigonal bipyramid
octahedral
A stands for the central atom, X4 is the number of bonds around the central
atom, and E2 is the number of lone pairs around the central atom. The lone
pairs would occupy the axial positions and the 4 bonds would occupy the
equatorial positions giving a square planar molecular geometry
The formal charge on the central
atom in XeO3 is
0
+1
+2
+3
-1
There are 26 valence electrons available for this compound. Xe is the
central atom. There are three bonding pairs from the oxygens and one lone
pair on the central atom. The free atom of Xe would have 8 valence electrons.
Subtract 2 for the lone pair electrons and 3 for each of the bonds from 8 and
The formal charge will be +3.
What would be the most likely
hybridization for a molecule of PCl5?
sp3
d2sp3
dsp2
sd3
dsp3
The 10 electrons in the expanded shell of P will hybridize from an s,
3 p orbitals, and one d orbital.
The occupancy or steric number on the
central atom in a molecule of SF4 is
5
4
3
2
1
The steric number or occupancy tells how many bonding pairs and lone
pairs are around the central atom. The S has 4 bonding pairs from the 4
fluorines and one lone pair.
The total number of molecular orbitals
formed is not equal to the number of
atomic orbitals that are initially present.
The number of molecular orbitals is always equal to the number of
atomic orbitals initially present
Which of the following two orbitals
would not have sufficient overlap to
form a molecular orbital?
py and px
s and s
s and pz
px and px
dzx and px
An orbital on the z axis would not overlap with an orbital on the x axis
sufficiently
Using MO theory how many unpaired
electrons would a molecule of B2 have?
0
1
2
3
4
B2 has 6 valence electrons: 2 in the σg orbital, 2 in the σu*, and 1 (unpaired)
in each of the two πu orbitals .
What is the bond order for a
molecule of F2?
0
.5
1
1.5
2
Bond order is ½ (# electrons in bonding orbitals-#electrons in
antibonding orbitals). F2 has 8 electrons in bonding orbitals and 6
electrons in antibonding orbitals.
Which of the following is NOT a
rule for forming molecular orbitals?
Each orbital must contain two electrons.
The number of molecular orbitals must equal the number of
atomic orbitals
The atomic orbitals must have the right symmetry
The atomic orbitals must have sufficient overlap
The atomic orbitals must have similar symmetry
Molecular orbitals do not have to be completely filled
O2 is diamagnetic.
The MO diagram of O2 shows 2 unpaired electrons in the πg* orbitals.
Unpaired electrons will make a molecule paramagnetic