(p 1 of 2)
1.
Most chemical bonds consist of electrostatic attractive forces and are called ____ bonds, or of shared electrons and are called _____bonds. a.
electric; shared b.
ionic; covalent c.
ionic; molecular d.
electronic; coordinate
2.
When electrons in a covalent bond are shared equally the bond is _________, but if the electrons are not shared equally the bond is
________, which means that it has a positive side and a negative side.
3.
When considering a bond between two atoms, the greater the difference in ____________, the more __________is the bond. a.
polarity; divided b.
atomic weight; nonpolar c.
electronegativity; polar d.
electronegativity; nonpolar
4.
Using Fig. 12.3 in the text, we see that the difference in electronegativity between hydrogen and iodine (4.0 – 2.5) = 1.5, which means that hydroiodic acid has a(n) ________________. a.
low boiling point b.
low acidity c.
unstable gas phase d.
dipole moment
5.
If we consider the electron configuration of strontium, [Kr]5s 2 , and that of oxygen, [He]2s 2 2p 4 , both atoms will c.
2 ; 2+ ; 1- ; SrO d.
2 ; 2- ; 2+ ; SrO
6.
The structures of ionic compounds are usually described as the packing of ____________ with smaller ____________ fitting into the interstices. a.
anions; cations b.
anions; electrons c.
cations; anions d.
cations; electrons attain stable noble gas electron configurations by the transfer of ____ electron(s). This will give Sr a charge of ___ and O a charge of ___. Hence the ionic compound formed has the formula
___________ and is named strontium oxide. a.
1 ; 1+ ; 1- ; SrO b.
2 ; 2+ ; 2- ; SrO
7.
Lewis structures show the arrangement of
________electrons in an atom or ion. a.
all b.
core c.
valence d.
missing
8.
In the Lewis structure for H
2
S there are a total of ______ electrons and ____ pair(s) of nonbonding electrons. a.
9 ; 2 b.
9 ; 1 c.
8 ; 2 d.
8 ; 1
9.
The Lewis structure for SO
2 contains ____ total electrons and____ nonbonding pairs of electrons, as well as one ______ bond and one _______ bond between the central sulfur and the oxygen atoms. a.
16 ; 4 ; single ; double b.
16 ; 6 ; single ; double c.
18 ; 4 ; single ; triple d.
18 ; 6 ; single ; double
10.
In the Lewis structure of the SO
2
molecule, the central S is connected to one O by a single bond and to the other O by a double bond. Does this mean that the two bonds in this molecule are different from each other? Explain!
11.
It is important to fully understand that Lewis structures are useful in determining the bonding relationships between atoms in a molecule, but that they do not directly provide a true picture of molecular shape. While the Lewis structure for methane, CH
4
, an important greenhouse gas, suggests a flat structure with 4 hydrogens arranged around a central carbon, the methane molecule is actually ________. a.
square planar b.
trigonal c.
tetrahedral d.
octahedral
12.
While the electron pair geometry of NH
3
is
_______, VSEPR predicts the molecular shape as
_________, due to the pair of nonbonding electrons on the central N. a.
tetrahedral; trigonal pyramidal b.
trigonal planar; tetrahedral c.
tetrahedral; trigonal planar d.
Both are trigonal planar.

(p 2 of 2)
13.
In determining the shape of the SO
2
molecule we examine the Lewis structure and find the central S atom attached to
O’s via one single and one double bond. The electron pair geometry is _______ and the molecular geometry is
_________, with bond angles of ____ degrees. a.
trigonal planar ; linear ; 180 b.
trigonal planar ; bent ; 120 c.
tetrahedral ; linear ; 120 d.
tetrahedral ; trigonal planar ; 120
1. Choice B properly identifies the bonds as ionic and covalent.
2. nonpolar; polar
3. Choice C correctly expresses the idea that bonds become more polar as the difference in the electronegativity of the atoms increases.
4. D associates the bond polarity of a diatomic molecule with having a dipole moment.
5. B correctly indicates the transfer of two electrons from strontium to oxygen to form the ionic compound known as strontium oxide.
6. A correctly describes the packing of anions (which tend to be larger) into specific patterns known as crystal lattices, while cations fit into the spaces or interstices between the packed anions.
7. C correctly indicates that only valence electrons are included in Lewis structures.
8. Choice C correctly describes the Lewis structure for hydrosulfuric acid: (6 electrons from S) + (2 x 1 = 2 electrons from H) = 8 total electrons. The Lewis structure is the same as that for H
9. D correctly describes the SO
2
O, with S in place of O.
2 molecule with (3 x 6 =) 18 electrons and S located between the two O’s with one single and one double bond.
10. No, the two bonds are not different. We invoke the concept of resonance to describe this structure. Both S to O bonds are identical and are intermediate between double and single bonds. Ozone, O
3 the same structure as SO
2
.
, which accumulates in the stratosphere and absorbs damaging UV radiation, has
11. C correctly describes the methane molecule as a tetrahedron, with the carbon centrally located in the geometric center and the 4 hydrogens forming the corners of the tetrahedron.
12. A correctly associates the 14 elements that make up the lanthanides with 14 available slots for electrons in the set of seven 4f orbitals.
1 answers both geometry questions correctly. The central N has four pairs of electrons around it, giving it a tetrahedral electron pair geometry.
But because one of the corners of the tetrahedron is an electron pair, the molecule is a trigonal pyramid with the N forming the apex and the three H’s forming the pyramidal base.
13. B correctly describes the electron pair about the central S as trigonal planar. S has one nonbonding electron pair, a single bond, and a double bond (counts as a single bond for shape). Because one corner of the triangle is occupied by an electron pair, the molecule has a bent shape with bond angles of 120 o .