Problem Set 3b
Due Nov 5th
Chemistry
Answer Key Chapter 8 Ionic Bonding
Test Tuesday November 16th
Score ____/36.75
Part 1: Ionic Compounds
1) Describe and diagram the process by which a neutral sodium atom becomes
positively charged. (1 point)
Na.  Na+1 + 1eThe sodium atom gives up one electron to form the Na+1 cation
2) Describe and diagram the process by which a neutral chlorine atom becomes
negatively charged.(1 point) ..
..
1e- + :Cl:

:Cl:
.
..
The chlorine atom gains one electron to form the Cl-1 anion.
3) Describe the concept of electroneutrality and how it applies to ionic crystals.
(1 point) Electroneutrality states that the overall number of electrons must
be maintained in any compound. The electrons that were on metals are
transferred to the non-metals to create the different charges of the ions. The
oppositely charged particles attract each other to form solid crystals.
4) What is lattice energy and how is it involved in an ionic bond? (1 point)Lattice
energy is the energy required to separate the ions of an ionic compound
wand is the energy given off when positive and negative ions attract. An
ionic bond is formed when anions and cations attract each other.
5) Using the concepts of ionic radii and lattice energy account for the trend in
melting points shown in the following table: (1 point)
Ionic Compound Melting Point Lattice Energy Ionic Radii
KF
858 oC
-808 kJ/mol
K+1 = 138 pm, F-1 = 133 pm
KCl
770 oC
-740 kJ/mol
K+1 = 138 pm, Cl-1 = 181 pm
KBr
734 oC
-671 kJ/mol
K+1 = 138 pm, Br-1 = 195 pm
o
KI
681 C
-632 kJ/mol
K+1 = 138 pm, I-1 = 220 pm
As the ionic radius of non-metal anions increases (F-1  I-1), the melting point and
lattice energy decrease. The larger the ion, the less energy is needed to hold the
substance in a solid phase, or in a crystalline structure.
6) Use the periodic table to predict the noble gas that is isoelectric with each of the
following ions.(0.25 points each 1.5 pts))
a. Br-1 Kr
b. Sr2+ Kr
c. Rb+ Kr d. Al3+ Ne e. I- Xe f. S2- Ar
7) What do atoms of a metal do to become a positively charged ion? What are these
positively charged ions called? (1 point) Atoms of a metal will give up some or
all of their valence electrons to become positively charged. They have a
positive charge because there are more protons than electrons in the new ion.
These ions are called cations.
8) What do atoms of a non-metal do to become a negatively charged ion? What are
these negatively charged ions called? (1 point) Atoms of a non-metal will gain
electrons to fill their valence energy level to become negatively charged.
They have a negative charge because there are more electrons than protons
in the new ion. These ions are called anions.
9) Give the charge that each of these metals forms when losing electrons to become
cations: .(0.25 points each 1pt))
a. Sodium (+1) b. Magnesium(+2) c. Aluminum(+3) d. Potassium(+1)
10) Give the charge that each of these non-metals forms when gaining electrons to
become anions: .(0.25 points each 1pt))
a. Fluorine (-1) b. Oxygen(-2) c. Phosphorous(-3)
d. Chlorine (-1)
11) What do the subscripts in a chemical formula tell you about the make up of the
ionic compound? What is the ratio of ions of sodium to the ions of oxygen in the
ionic compound sodium oxide? .(1 point)The subscripts show the lowest whole
number ratio of ions in a neutral ionic compound. The ratio of sodium
cations to oxide anions is 2 to 1 in the ionic compound sodium oxide.
12) Why are roman numerals used to name some ionic compounds, like copper (II)
chloride, but not used to name others, like sodium chloride? (1 point)The roman
numerals are used to indicate the charge of the cation in any ionic compound
that has a metal that can take multiple oxidation states. Many ionic
compounds have cations that take only one oxidation state, and that value
does not need to be represented with a roman numeral.
13) Name the following binary ionic compounds. .(0.25 points each 1pt))
(Hint: None of these contain roman metals)
a. NaI
b. CaBr2
c. Mg3P2
d. Al2O3
a. sodium iodide
b. calcium bromide
c. magnesium phosphide
d. aluminum oxide
14) Name the following binary ionic compounds. .(0.25 points each 1pt))
(Hint: All of these contain roman metals)
a. CuI
b. CrBr3
c. Au3P
d. PtO2
a. copper (I) iodide
b. chromium (III) bromide
c. gold (I) phosphide
d. platinum (IV) oxide
15) Name the following binary ionic compounds. .(0.25 points each 1pt))
(Hint: Some of these contain roman metals)
a. Sr3N2
b. CuBr2
c. RbCl
d. CoO
a. strontium nitride
b. copper (II) bromide
c. rubidium chloride
d. cobalt (II) oxide
16) Give the formula for the following binary ionic compounds. .(0.25 points 2pt))
a. sodium sulfide Na2S
e. lithium bromide LiBr
b. magnesium oxide MgO
f. aluminum fluoride AlF3
c. manganese (III) iodide MnI2
g. iron (II) chloride FeCl2
d. vanadium (II) nitride V3N2
h. copper (I) phosphide Cu3P
17) Compare AND contrast binary ionic compounds to ternary ionic compounds. (1
point) Binary ionic compounds and ternary ionic compounds are both made
of cations and anions that attract each other to generate a crystalline
structure. Binary ionic compounds are made of only two types of element,
while ternary ionic compounds have at least three different elements in them
(typically oxygen is one of the elements.) Ternary ionic compounds have one
polyatomic ion in the structure.
18) Why are parenthesis used in writing a formula of an ionic compound with a
polyatomic ion? (example: Ca(OH)2 = calcium hydroxide) (1 point)Parenthesis
are used to separate the ions and show that there are multiple polyatomic
ions in the formula and the crystalline structure. In the example Ca(OH)2
there are two hydroxide (OH-1) anions for every one calcium (Ca+2) cation.
19) Name the following ternary ionic compounds..(0.25 points each 1pt))
a. NaIO3
b. NH4Br
c. K2CO3
d. Ba(CN)2
a. sodium iodate
b. ammonium bromide
c. potassium carbonate
d. barium cyanide
20) Name the following ternary ionic compounds. .(0.25 points each 1pt))
a. CuIO3
b. Cr(BrO3)3
c. AuOH
d. PtSO4
a. copper (I) iodate
b. chromium (III) bromate
c. gold (I) hydroxide
d. platinum (II) sulfate
21) Name the following ternary ionic compounds. .(0.25 points each 1pt))
a. Sr(NO3)2
b. Cu(C2H3O2)2
c. RbClO4
d. CrPO4
a. strontium nitrate
b. copper (II) acetate
c. rubidium perchlorate
d. chromium phosphate
22) Give the formula for each of these ternary ionic compounds: .(0.25 points 2pt))
a. sodium sulfate Na2SO4
e. barium phosphate Ba3(PO4)2
b. sodium sulfite Na2SO3
f. calcium hydroxide Ca(OH)2
c. copper (II) chlorate Cu(ClO3)2
g. calcium acetate Ca(C2H3O2)2
d. copper (I) chlorite CuClO2
h. calcium carbonate CaCO3
23) What subscripts would be used if an ionic compound (0.25 points each 1.25pt))
a. Between an alkali metal and a halogen 1: 1
b. Between an alkaline earth metal and a halogen 1 : 2
c. Between an alkali metal and the oxide anion 2:1
d. Between an alkaline earth metal and an oxide anion 1:1
e. Between a group 3A element and a halogen. 3:1
Multiple choice Ionic Compounds (1 point each)
24) The alkaline earth metals take “this” charge when forming “these” ions
a. +2 , cations b. +1, cations
c. –2, anions d. –1 anions
25) The alkali metals take “this” charge when forming “these” ions
a. +2 , cations b. +1, cations
c. –2, anions d. –1 anions
26) The halogens take “this” charge when forming “these” ions
a. +2 , cations b. +1, cations
c. –2, anions d. –1 anions
27) Which of the following is a binary ionic compound?
a. H2O
b. NaClO3
c. MgCl2
d. C6H12
28) Which of the following is a ternary ionic compound?
a. H2O
b. NaClO3
c. MgCl2
d. C6H12O
29) Which of the following compounds is properly named copper (II) oxide?
a. CuO
b. Cu2O
c. CuO2
d.Cu2O2
30) Which of the following requires a roman numeral in its name?
a. BaCl2
b. BeCl2
c. BCl3
d. NbCl3
31) What is the whole number ratio of sodium cations to sulfate anions in a sample of
sodium sulfate?
a. 1:2
b. 1:1
c. 2:1
d. 3:1
32) Define a metallic bond. How does it differ from an ionic bond? (1point) Metallic
bonds utilize the sea of electrons that metals have between their cations to
hold the ions in place, while allowing some sliding and shifting. This mobility
is far different from ionic bonds because crystalline structures of ionic
compounds are very rigid and far less mobile than the particles in a metal.
33) Why does an applied force (like hitting a piece of metal with a hammer) cause
metal ions to move? What unique properties of metals are due to this mobility?
(1 point) The applied force allows the metal ions to move because the ions are
not strictly confined by bonds. The metallic bonds between the ions are
mobile. This allows most metals to be malleable and ductile.
34) In a previous lab we used a hammer to tap samples of elements. How did you
determine if a substance was a metal or a non metal with this test? What
properties of metals do most ionic compounds and most molecular compounds
not have? (1 point) Metals are malleable and non-metals are brittle. Hitting
them with a hammer will show how well the substance responds to a force
and if the ions are allowed to slide and shift – or shatter.
Part 2 Molecular compounds
35) What makes molecular compounds different from ionic compounds? Which
elements are typically found in molecular compounds? Molecular compounds
are formed when electrons between two non-metals (or hydrogen) are
shared. There is no transfer of electrons in a molecular compound. Also –
each molecule of substance exists alone – the ionic crystals are connected one
to the next, that is not true of molecules. The non-metals are found in
molecules.
36) How many electrons are shared in…
a. A single covalent bond 2
b. A double covalent bond 4
c. A triple covalent bond 6
d. A quadruple covalent bond 8
e. A coordinate covalent bond 2
37) What happens to bond length as more and more electrons are shared in a bond?
Which is a longer bond: a single bond, a double bond or a triple bond? Why?
As more and more electrons are added to a bond, the nuclei of the atoms in
the bond are drawn closer and closer together. This decreases the bond
length and the energy of the bond increase. A triple bond will be the shortest
measured bond assuming the atomic radii are similar in value.
38) What is a sigma () bond? What is a pi () bond? A sigma bond occurs when
an s orbital overlaps with another s orbital or with a p orbital. A pi bond
occurs when two p orbitals overlap. Overlapping orbitals show which two
electrons are being shared.
39) Name the following molecular compounds:
a. CO2 b. PF3
c. SiBr4
d. N2O4
e. PCl5
a. carbon dioxide
b. phosphorous tribromide
c. silicon tetrabromide d. dinitrogen tetroxide
e. phosphorous pentachloride
40) Give the formula for the following molecular compounds:
a. sulfur dioxide SO2
d. diselenium heptoxide Se2O7
b. nitrogen triiodide NI3
e. chlorine heptabromide ClBr7
c. carbon monoxide CO
f. carbon tetrachloride CCl4
41) Why is the formula for “tricarbon monophosphourous monoxide” of great
cinematographic importance for sci-fi films? C3PO is a leading role in the Star
Wars series
42) How many atoms of nitrogen are there in a molecule of TNT: C6H3(NO2)3? 3
43) Draw the Lewis Dot diagram for these elements: C, N, O, F
.
.
.
..
.C.
.
:N
:O:
:F:
.
.
.
.
44) Draw the Lewis Dot Diagram for these molecular compounds. The underlined
elements are the central atom in the molecule.
a. Cl2
b. H2S
c. CH2Cl2
d. SiS2..
:Cl:
.. ..
..
..
..
|
a. :Cl-Cl:
b
H-S-H
c.
H
–
C
–
H
d.
S=Si=S
.. ..
..
..
..
|
:Cl:
..
45) What is a coordinate covalent bond? Explain how carbon monoxide is able to
follow the octet rule even though carbon only has four valence electrons and a
quadruple bond is not formed. A coordinate covalent bond is a chemical bond
between two atoms where one atom donates the two electrons to be shared in
the bond – it is still a covalent bond because once donated the two electrons
are shared by the two atoms. Carbon monoxide forms a coordinate covalent
bond because carbon only has 4 valence electrons and oxygen has 6 – there is
a triple bond formed (one sigma and two pi bonds) – the second pi bond’s
electrons both came from the oxygen atom.
:C=O:
46) What are resonance structures? Resonance structures are drawings of the
possible arrangements of the pi bonds in a compound. The molecule actually
switches very quickly (resonates) between its different resonance structures.
47) Draw at the correct resonance structures of …
a. Ozone (O3)
b. Carbonate (CO3-2)
.. .. ..
:O-O=O:
..
.. .. ..
:O=O-O:
..
c. Sulfate (SO4-2)
..
..
.x
..
-2
:O:
-2
:O:
-2
:O:
-2
:O:
.. | ..
.. | ..
.. | .x
.. | ..
:O-C=O:
:O=C-O:
:O-S-O:
:O-S-O:
..
..
.. | ..
.. .x
:O:
-2
:O:
:O:
.. || ..
..
..
.x
.x
:O-C-O:
:O:
:O:
-2
..
..
.x | . x
.. | .. -2
:O-S-O:
:O-S-O:
.. | ..
.. | ..
:O:
:O:
..
.x
note – SO4-2 are all the same
tetrahedron with two extra e-
48) Use the chart of electronegativities to determine if the following compounds have
ionic bonds, polar covalent bonds, or non-polar covalent bonds.
a. H and O polar covalent
d. Si and B non-polar covalent
b. As and P non-polar covalent
e. Ca and O ionic
c. C and Cl polar covalent
49) Draw the electron density cloud for these molecular compounds.
a. H2
b. HCl
c. H2O
d. CCl4
O
H-H
H-Cl
H
H
Cl
Cl c Cl
Cl
50) What does the electron density cloud represent? The electron density cloud
represents the electron orbitals after they have formed covalent bonds. Polar
covalent bonds will appear as asymmetric clouds, while non-polar covalent
bonds will have perfect symmetry as a shape.
51) What do the letters VSEPR stand for in VSEPR theory? Valence Shell Electron
Pair Repulsion - this theory suggests that the valence electron pairs in a
compound will repel other pairs because both pairs will have negative
charges.
52) What is a tetrahedron? How is it possible to describe CH4, NH3 and H2O as
having a tetrahedral electronic geometry? Draw each molecule as a 3-D figure.
A tetrahedron is a symmetric four sided 3-dimensional form. All three of
those molecules have four pairs of electrons off the central atom and
therefore the electronic geometry is tetrahedral, but the molecular geometry
will be: CH4 – tetrahedral, NH3 – trigonal pyramidal, H2O – linear bent
H
C
H HH
..
N
H HH
.. ..
O
H H
53) Why is the bond angle in water (106o) smaller than the bond angle in methane
(109.5o) if they both have tetrahedral electronic geometries? The 2 lone pairs of
electrons off the central oxygen atom force the 2 pairs bonded electrons
between the oxygen and hydrogen towards each other (away from the nonbonded electron pairs). In methane the bonds repel each other equally.
54) Draw an appropriate 3-D drawing based upon the VSEPR theory for…
See page 260 for text images
a. BeCl2 linear c. BF3 trigonal planar
e. carbon tetrachloride
tetrahedral
Cl-Be-Cl
F
F
Cl
B
C
Cl Cl Cl
F
b. Ammonia
Trigonal pyramidal
..
N
H HH
d. water
linear bent
.. ..
O
H
H
f. sulfur hexachloride
octahedral
Cl
Cl
Cl
S
Cl
Cl
Cl
Part 3 - Acids
55) Discuss acids and bases in a couple of sentences. Be sure to explain the following
topics in specific, scientific terms: Acids and bases are ionic compounds that
are identified by their ions. Acids, as we know them now, have a hydrogen
cation. Bases, as we know them now, have hydroxide as their anion.
a) The prefix and the suffix of binary acids A binary acid, like HCl, is
named hydro-chlor-ic acid. The prefix “hydro-” shows that the acid is
a binary substance, and the “-ic” suffix shows that the substance is an
acid.
b) Why “ates are icky” or where the “termites are in your house and not in
your ate-ic (attic).” The odd phrases “ates are icky” and “termites are
in your house and not in your ate-ic.” Are meant to serve as verbal
reminders of how the ternary acids are named. If the polyatomic
anion ends with “-ate” the acid ends with “-ic”, while if the
polyatomic anion ends with “-ite” the acid ends in “-ous.”
c) how the name can be translated into the correct formula Changing from a
name of an acid or a base to its formula follows the principle of
electroneutrality. Because acids and bases are ionic compounds, the
overall charge on the compounds must be neutral, so the cations
charge will be equal and opposite the anions charge.
d) specifically how a ternary acid, like H2SO3, is named. To name H2SO3
the name of the anion SO3-2 is sulfite so the name of the acid is sulfous
acid.
56) Give the formula for each of the following acids
a) hydrochloric acid HCl b) hydrophosphoric acid H3P
d) nitrous acid
HNO2
c) carbonic acid H2CO3
57) Give the name for each of the following acids and bases.
a) HI-hydroiodic acid
b) H2SO3 sulfous acid
c) HC2H3O2 acetic acid
d) H2Se hydroselenic acid e) LiOH lithium hydroxide
58) Compare and contrast hypochlorous acid (HClO) with perchloric acid (HClO4) in
as much detail as possible. Both are ternary ionic compounds. The chlorine
atom in the hypochlorous acid has only one oxygen atom – this is one less
than the number of oxygen atoms in chlorous acid (hence the hypo-). The
chlorine atom in the perchloric acid has four oxygen atoms one more than
the number of oxygen atoms in chloric acid (hence the per-).
59) Identify the following as:
binary acids (BA)
binary ionic compounds (BIC)
ternary acids (TA)
molecular compounds (MC).
ternary ionic compounds (TIC)
ionic compounds with multiple charge metals (ICMC)
a) CO2
MC
b) H2SO4
TA
c) LiI
BIC
d) Be(NO2)2
TIC
e) MoO
ICMC
f) HCl
BA
g) MoO2
ICMC
h) MgCl2
BIC
i) Sr(NO3)2
TIC
j) (NH4)2O
TIC
k) HBr
BA
l) NaF
BIC
m)C6H12O6
MC
n) H2CO3
TA
o) FeCl6
ICMC
p) CH2O
MC
q) TiCl4
ICMC
r) PbO
ICMC
60) True Formula Test… give the formula of each of the following substances…
there are molecular compounds, binary ionic compounds, ternary ionic
compounds and roman metal compounds all mixed in… good luck
a.
b.
c.
d.
e.
f.
g.
potassium nitrate KNO3
iron (III) oxalate Fe2(C2O4)3
perchloric acid HClO4
rubidium sulfide Rb2S
carbon tetrachloride CCl4
hydrochloric acid HCl
sulfuric acid H2SO4
h.
i.
j.
k.
l.
m.
n.
copper (I) oxide Cu2O
beryllium hydroxide Be(OH)2
sulfur hexabromide SBr6
magnesium oxide MgO
acetic acid HC2H3O2
diphosphorous pentoxide P2O5
hydrogen hydroxide H2O
61) Write the name and formula of any binary ionic compound. lithium iodide LiI
62) Write the name and formula of any ternary ionic compound. Lithium iodate
LiIO3
63) Write the name and formula of any Roman Metal compound. Tin (II) oxide SnO
64) Write the name and formula of any molecular compound. Carbon disulfide CS2
65) Write the name and formula of any binary acid hydrochloric acid HCl
66) Write the name and formula of any ternary acid. Chloric acid HClO3