1
Review: Density
• The density of silver is 10.5 g/cm3. What is the
volume of a piece of Ag that contains 2.8 ×
1022 atoms?
• a. 0.48 cm3
• b. 53 cm3
• c. 4.8 × 10-2 cm3
• d. 2.1 cm3
• What is the length of 1 side?
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
Chemistry and Chemical Reactivity
6th Edition
2
John C. Kotz
Paul M. Treichel
Gabriela C. Weaver
CHAPTER 3
Molecules, Ions and Their Compounds
Lectures written by John Kotz
Kull Spring 2007 Chem 105 Lsn 4
©2006
2006
Brooks/Cole
Thomson
©
Brooks/Cole
- Thomson
3
3.1 Molecules, Compounds, &
Formulas
• COMPOUNDS are a combination of 2 or
more elements in definite ratios by mass.
• The character of each element is lost when
forming a compound.
• MOLECULES are the smallest unit of a
compound that retains the characteristics of
the compound.
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
Glycine
3.2 FORMULAS and
3.3 Molecular Models
4
• Molecular Formula: C2H5NO2
• Condensed Formula
H2NCH2COOH
to show atom ordering
• structural formula
H H O
H N C C O H
H
Ball & stickKull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
Space-filling
3.3 Ionic compounds: Formulas,
names, and Properties
• Ionic charges (use periodic table)
– Desire for noble gas configuration
– Cations (+)
– Anions (-)
• 3.6 What charges are most commonly
observed for monatomic ions of the following
elements?
(a)Selenium
(b) fluorine
(c) Iron
(d) nitrogen
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
5
Charges on Common Ions
-4 -3 -2 -1
+1
+2
+3
By losing or gaining e-, atom has same
number of e-’s
Group
8A atom.
Kullas
Springnearest
2007 Chem 105 Lsn
4
© 2006 Brooks/Cole - Thomson
6
IONIC COMPOUNDS
NH4
7
+
Cl
Name derived
by adding -ide
to stem
ammonium chloride, NH4Cl
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
8
Note: many O
containing anions
have names ending
in –ate (or -ite).
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
Table 3.1, page 107.
Some Ionic Compounds
Ca2+ + 2 F- ---> CaF2
Mg2+ + NO3- ---->
Mg(NO3)2
magnesium nitrate
Fe2+ + PO43- ---->
calcium fluoride
Fe3(PO4)2
iron(II) phosphate
(See CD, Screen 3.11 for naming practice)
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
9
Properties of Ionic Compounds
Forming NaCl from Na and Cl2
• A metal atom can
transfer an electron to
a nonmetal.
• The resulting cation
and anion are
attracted to each
other by
electrostatic
forces.
• These forces are governed by
COULOMB’S LAW.
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
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Electrostatic Forces
COULOMB’S LAW
Active Figure 3.10
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
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12
Importance of Coulomb’s Law
NaCl, Na+ and Cl-,
m.p. 804 oC
MgO, Mg2+ and O2m.p. 2800 oC
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
13
NONMETALS
NONMETAL + n e- ------> Xnwhere n = 8 - Group no.
Group 4A
Group 5A
Group 6A
Group 7A
C4-,carbide N3-, nitride O2-, oxide F-, fluoride
Name derived
by adding -ide
to stem
S2-, sulfide Cl-, chloride
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
Br-, bromide
I-, iodide
14
3-14 For each of the following
compounds, give the formula,
charge, and the number of each ion
that makes up the compound.
(a)K2S
(b)CoSO4
(c)CuCO3
(d)Ti(SO4)2
(e)KH2PO4
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
15
3-16 Platinum is a transition
element and forms Pt2+ and Pt4+
ions. Write the formulas for the
compounds of each of these ions
with (a) chloride ions and (b) sulfide
ions.
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
3.4 Molecular Compounds
Compounds without Ions
CO2 Carbon dioxide
CH4 methane
BCl3
boron trichloride
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
All are
formed from
two or more
nonmetals.
Ionic
compounds
generally
involve a metal
and nonmetal
(NaCl)
16
17
ELEMENTS THAT EXIST AS
MOLECULES
Allotropes
ofLsn C
Kull Spring 2007 Chem 105
4
© 2006 Brooks/Cole - Thomson
ELEMENTS THAT EXIST AS
DIATOMIC MOLECULES
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
18
ELEMENTS THAT EXIST AS
POLYATOMIC MOLECULES
19
S8 sulfur
molecules
White P4 and polymeric
red phosphorusKull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
3.5 Formulas, Compounds, and the mole
grams/moles/somethings
20
How many moles of alcohol are there in
a “standard” can of beer if there are
21.3 g of C2H6O?
a) Molar mass of C2H6O = 46.08 g/mol
1 mol
(b) Calc. moles of alcohol
21.3 g •
= 0.462 mol
46.08 g
How many molecules of
alcohol are there in a “standard” can of
beer if there are 21.3 g of C2H6O?
6.022 x 1023 molecules
0.462 mol •
1 mol
2007 Chem 105 Lsn 4
= 2.78 x 10Kull23Spring
molecules
© 2006 Brooks/Cole - Thomson
How many atoms of C are there in
a “standard” can of beer if there are
21.3 g of C2H6O?
There are 2.78 x 1023 molecules.
Each molecule contains 2 C atoms.
Therefore, the number of C atoms is
23
2.78 x 10
2 C atoms
molecules •
1 molecule
= 5.57 x 1023 C atoms
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
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22
3-22 Give the formula for each of
the following ionic compounds.
(a) Calcium hydrogen carbonate
(b) Potassium permanganate
(c) Magnesium perchlorate
(d) Potassium hydrogen phosphate
(e) Sodium sulfite
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
3-34 Calculate the molar mass of
each hydrated compound. Note
that the water of hydration is
included in the molar mass.
(a) H2C2O4  2 H2O
(b) MgSO4  7 H2O
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
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3-36 Assume you have 0.123 mol of
each of the following compounds.
What mass of each is present?
(a) C14H10O4, benzoyl peroxide
(b) Pt(NH3)2Cl2, cisplatin
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
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3-66 The compound (NH4)2SO4
consists of two polyatomic ions.
What are the names and electric
charges of these ions? What is the
molar mass of this compound?
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
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68
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson
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88
Kull Spring 2007 Chem 105 Lsn 4
© 2006 Brooks/Cole - Thomson