Introduction to Bonding

Bonding is the joining of two atoms in a stable

arrangement.
Elements will gain, lose, or share electrons to attain
the electron configuration of the noble gas closest
to them in the periodic table.

There are two different kinds of bonding:

•Ionic bonds result from the transfer of electrons
from one element to another.
•Covalent bonds result from the sharing of
electrons between two atoms.
1
 Introduction to Bonding
Ionic bonds form between:
•a metal on the left side of the periodic table
•a nonmetal on the right side of the periodic table

Na + Cl2 NaCl

sodium chlorine sodium chloride

metal gas crystals
2
 Introduction to Bonding
Covalent bonds are formed when two nonmetals
combine, or when a metalloid bonds to a nonmetal.

A molecule is a discrete group of atoms that share

electrons.

3
 Ions
Cations and Anions

• Ions are charged species in which the number

of protons and electrons in an atom is unequal.

• Ionic compounds consist of oppositely charged

ions that have a strong electrostatic attraction
for each other.

•There are two types of ions—cations and anions.

4
 Ions
Cations and Anions
Cations are positively charged ions. A cation has
fewer electrons (e−) than protons.

5
 Ions
Cations and Anions
Anions are negatively charged ions. An anion has
more e− than protons.

6
 Ions
The Octet Rule

By losing or gaining one, two, or three electrons, an atom

forms a completely filled outer shell of e−.

The octet rule: a main group element is especially

stable when it possesses an octet of e− in its outer
shell.

octet = 8 valence e−

7
 Ionic Bonding
NaCl

n=3

n=2
-
n=3
-
- - - - -
-
-
-
- - - - -
-
+ -

- - -
- - -
-
- - - - - -
- -

Na Cl Na+ Cl-
[Ne]3s1 [Ne]3s23p5 [Ne] [Ne]3s23p6

Transfer of electrons to achieve a stable octet (8 electrons in valence shell).

 sodium metal and chlorine gas react to form sodium chloride

2 Na + Cl2 2 NaCl
Copyright © 2007 Pearson Benjamin Cummings. All rights reserved.
Ionic Bonds
–A positively charged ion (cation)
is attracted to a negatively
charge ion (anion)
 Ions
Relating Group Number to Ionic Charge for
Main Group Elements
•Elements in the same group form ions of similar
charge.
•Metals form cations.

•For metals in groups 1A, 2A, and 3A, the group

number = the charge on the cation.

•Nonmetals form anions.

•For nonmetals in Groups 6A and 7A, the anion

charge = 8 – the group number.
11
 Ions
Relating Group Number to Ionic Charge for
Groups 1A–3A
the cation charge = the group number

group 1A: M M + + e−
1 valence e−

group 2A: M M2+ + 2e−

2 valence e−

group 3A: M M3+ + 3e−

3 valence e−
12
 Ions
Relating Group Number to Ionic Charge for
Groups 6A and 7A
the anion charge = 8 – group number

group 6A: X + 2e− X 2−

6 valence e−

group 7A: X + e− X −

7 valence e−

13
 Ions
Ions Formed by the Main Group Elements

14
 Ions
Metals with Variable Charge

15
 Ions
Common Ions in the Human Body

16
 Ionic Compounds
Formulas for Ionic Compounds

The sum of the charges in an ionic compound must

be zero overall.

17
 Ionic Compounds
Formulas for Ionic Compounds

18
 Ionic Compounds
HOW TO Write a Formula for an Ionic Com-
pound
Step Identify which element is the cation
[1] and which is the anion.
•Metals form cations and nonmetals form anions.

•Use the group number of a main group element

to determine the charge.

K+ Cl− Ca 2+ O 2−
metal nonmetal metal nonmetal
group 1A group 7A group 2A group 6A
19
 Ionic Compounds
HOW TO Write a Formula for an Ionic Com-
pound
Step Criss-cross rule!
[2]
charge on cation / anion
“becomes” subscript of anion / cation

Al 3+
and O 2–

Al2 O3
Al2O3
Criss-Cross Rule
Ba2+ and S2–

Ba2 S2
BaS
Criss-Cross Rule
In 3+
and Br 1–

In1 Br3
InBr3
 Ionic Compounds
HOW TO Write a Formula for an Ionic Com-
pound
Step To write the formula, place the cation
[3] first and then the anion, and omit charges.

Al3+ and O2– Ba2+ and S2– In3+ and Br1–

Al2 O3 Ba2 S2 In1 Br3

Al2O3 BaS InBr3

** Warning: Reduce to lowest terms. 23

Try this!: Write the chemical formula for the
following:
1.silver and nitride
2.zinc and sulfide
3.aluminum and sulfide
4.iron (III) and oxide

24
 Naming Ionic Compounds
Binary Compounds

To name binary compounds, give the

name of metal followed by the name
of the non-metal, with the ending re-
placed by the suffix –ide.

Examples:
NaCl sodium chloride
Examples:

CaS calcium sulfide

AlI3 aluminum iodide

 Naming Ionic Compounds
Naming Cations

Main group cations are named for the element from

which they are formed.

Na+ K+ Ca2+ Mg2+

sodium potassium calcium magnesium

27
 Ions
Ions Formed by the Main Group Elements

28
 Ions
Metals with Variable Charge

29
 Naming Ionic Compounds
Naming Cations
Other cations can be named two ways:
•Stock name: Follow the name of the cation
by a Roman numeral in parenthesis to indicate
its charge.

Fe2+ Fe3+
iron(II) iron(III)
•Classical name: Use suffix “-ous” for the cation
with a smaller charge and suffix “-ic” for the
cation with a higher charge.

Fe2+ Fe3+
ferrous ferric
30
Naming Ionic Compounds

31
 Naming Ionic Compounds
Naming Anions
Anions are named by replacing the ending of the
element name by the suffix “-ide.”

32
 Naming Ionic Compounds
Compounds of Main Group Metals
HOW TO Name an Ionic Compound That Con-
tains
Main Group Metals
•Name the cation and then the anion.

Na+ + F− NaF
sodium fluoride sodium fluoride

Mg2+ + Cl− MgCl2

magnesium chloride magnesium chloride

33
 Naming Ionic Compounds
Compounds of Metals with a Variable Charge
HOW TO Name an Ionic Compound That Con-
tains
a Metal with Variable Charge
Exam- Give the name for CuCl2.
ple
Step
Determine the charge on the cation.
[1]
CuCl2

cation anion
Cu +2 Cl−
34
 Naming Ionic Compounds
Compounds of Metals with a Variable Charge
HOW TO Name an Ionic Compound That Con-
tains
a Metal with Variable Charge
Step
Name the cation and the anion.
[2]
•cation is named one of two possible ways:
Stock Classical
Cu2+ copper(II) cupric

•anion changes ending of element name to “-ide”

Cl− chloride
35
 Naming Ionic Compounds
Compounds of Metals with a Variable Charge
HOW TO Name an Ionic Compound That Con-
tains
a Metal with Variable Charge
Step Write the name of the cation first, then
[3] the anion.
CuCl2

copper(II) chloride

Answer = or

cupric chloride
36
 Naming Ionic Compounds
Writing a Formula from the Name
HOW TO Derive a Formula from the Name of an Ionic
Compound

Exam-
Write the formula for tin(IV) oxide.
ple
Step Identify the cation and anion and
[1] determine their charges.

tin(IV) oxide
Sn4+ O 2−

37
 Naming Ionic Compounds
Writing a Formula from the Name
HOW TO Derive a Formula from the Name of an Ionic
Compound

Step
[2] Criss-cross.
Sn4+ O2−

Step Write the formula with the cation first.

[3] Simplify!
final answer = SnO2

38
 Polyatomic Ions
A polyatomic ion is a cation or anion that contains
more than one atom.

39
 Polyatomic Ions
Writing Formulas for Ionic Compounds with
Polyatomic Ions

tin (II) sulfate tin (II) sulfite tin (IV) sulfate

Sn2+ SO42- Sn2+ SO32- Sn4+ SO42-

SnSO4 SnSO3 Sn2(SO4)4

Sn(SO4)2
 Polyatomic Ions
Writing Formulas for Ionic Compounds with
Polyatomic Ions
Parentheses are required only when you need more
than one “bunch” of a particular polyatomic ion.

Ba2+ and SO42– BaSO4 barium sulfate

Mg2+ and NO21– Mg(NO2)2 magnesium nitrite

NH41+ and ClO31– NH4ClO3 ammonium chlorate

? Sn4+ and SO42– Sn(SO4)2 tin (IV) sulfate

Fe3+ and Cr2O72– Fe2(Cr2O7)3 iron (III) dichromate

NH41+ and N3– (NH4)3N ammonium nitride

 Polyatomic Ions
Writing Formulas for Ionic Compounds with
Polyatomic Ions

Write formulas:

iron (III) nitrate Fe3+ NO31– Fe(NO3)3

ammonium phosphide NH41+ P3– (NH4)3P
ammonium chlorite NH41+ ClO21– NH4ClO2
zinc phosphate Zn2+ PO43– Zn3(PO4)2
lead (II) permanganate Pb2+ MnO41– Pb(MnO4)2
Try this! Write the chemical formula for
the following:
1.calcium and carbonate
2.ammonium and sulfide
3.ammonium and nitrate
 Polyatomic Ions
Naming Ionic Compounds with Polyatomic Ions
The same rules are followed for naming standard
ionic compounds:

• Name the cation and then the anion.

NaHCO3 Al2(SO4)3
sodium bicarbonate aluminum sulfate
or
sodium hydrogen carbonate

44
Physical Properties of Ionic Compounds
•Ionic compounds are crystalline solids that have
very high melting points (NaCl = 801 oC) and
extremely high boiling points (NaCl = 1413 oC).
•When ionic compounds dissolve in water, they
separate into cations and anions. The resulting
aqueous solutions conduct an electric current.

+ 

NaCl water solution

45
 Quiz 2: Writing and Naming Binary Com-
pounds
1 BaO ____________________

2 ________________ sodium bromide

3 MgI2 ____________________

4 KCl ____________________

5 ________________ strontium fluoride

 Quiz 2: Writing and Naming Binary Com-
pounds
6 AgBrO3 ____________________

7 ________________ ammonium nitride

8 Al2(CrO4)3 ____________________

9 Cr2(SO3)3 ____________________

10 ________________ ammonium thiosulfate

 Quiz 2: Writing and Naming Binary Com-
pounds
1 BaO barium oxide
____________________
NaBr
2 ________________ sodium bromide

3 MgI2 magnesium iodide

____________________

4 KCl potassium chloride

____________________
SrF2
5 ________________ strontium fluoride
 Quiz 2: Writing and Naming Binary Com-
pounds
6 AgBrO3 silver bromate
____________________

(NH4)3N
7 ________________ ammonium nitride
aluminum chromate
8 Al2(CrO4)3 ____________________

chromium (III) sulfite

9 Cr2(SO3)3 ____________________
(NH4)2S2O3
10 ________________ ammonium thiosulfate