Ionic bonding results from the electrostatic attraction between oppositely charged ions. When a metal atom reacts with a nonmetal, the metal typically loses electrons to form a cation while the nonmetal gains electrons to form an anion. These oppositely charged ions are then attracted to each other, forming an ionic bond. Ionic compounds have crystalline structures where the ions are arranged in repeating patterns. Their strong ionic bonds make them brittle with high melting points. Many ionic compounds dissolve in water to form electrolyte solutions where the ions are free to move.

1. Compounds and
Bonding
Ionic Bonding

2. Chemical bonds are the “glue” that hold groups of atoms
together. Some bond “facts”:
All bonds form because of an electrostatic attraction
between the positive and negative charges.
IONIC and COVALENT
Chemical bonds are classified in TWO categories
Energy is required to break chemical bonds. Energy
is released when bonds form.

3. BONDING IS ALL ABOUT ELECTRONS
Recall: Electron configurations

4. To understand bonding you must have a very clear
idea about valence electrons
Lewis dot diagrams are used to illustrate the
number of valence electrons for an atom:
1. Determine the number of valence electrons.
2. Write the element symbol
3. Place one dot to represent electrons around the
four sides of the element symbol. Do not place
two electrons together until each side has one
(exception is helium).

5. Lewis Dot structures – complete on the first worksheet

6. The basis for an ionic bond is the electrostatic
attraction between two oppositely charged ions.
ATTRACTIVE FORCE
+ HOLDS IONS
TOGETHER
-
Cation (metal) Anion (non-metal)
Positive ion Negative ion
Has “lost” electrons Has “gained”
electrons

7. When metallic elements react with non-metallic
elements . . . .
Metal atoms have a tendency to lose valence
electrons and form positive ions.
Non-metals have a tendency to gain valence
electrons and form negative ions.
Mg
Mg+2 Cl
Cl-1
To be most stable, atoms form ions by gaining or losing electrons so
as to complete the outer valence shell. This usually means 8
electrons so the rule is called the OCTET RULE.

8. The electrostatic attraction between the positive
magnesium and negative chloride ions is the basis for
the ionic bond.
Mg2+ Cl-
Notice that the overall electrical charge of the Mg-Cl
combination is still +1. THE CHARGES ARE NOT
BALANCED! (neutral)

9. The electrical charges will be balanced if two chloride
ions combine with the magnesium ion.
This is a convenient combination as the Mg atom has lost
2 electrons whereas each chlorine atom gained 1.
Cl- Mg2+ Cl-
This combination is the formula unit for the compound
and has the formula MgCl2

10. The electrical charge is always balanced in the chemical
formula of an ionic compound.
For example – what ionic compound forms between
calcium and bromine?
1. Locate the elements involved on the Periodic Table

11. 2. Determine the ions that are formed by each element
calcium is in group II : loses 2 e- to become Ca2+
bromine is in group VII: gains 1 e- to become Br-1
3. Criss-cross the oxidation number (charge) to find the
numbers of each atom in the compound. You may need to
simplify.
Ca2+ Br-1
CaBr2

12. Write the chemical formula for calcium oxide
1. Locate the elements involved on the Periodic Table
2. Determine the ions that are formed by each element
calcium is in group II : loses 2 e- to become Ca2+
oxygen is in group VI: gains 2 e- to become O-2
3. Criss-cross the ionic charges and simplify.
Ca 2+ O -2
CaO

13. Ionic Bonding Worksheet
Review ion formation, the octet rule, determining the number of
protons, neutrons and electrons in atoms or ions AND showing
ionic bonding with dot diagrams
See WIKI for answers

14. Naming Ionic Compounds
We know how to write the chemical formula of a simple ionic
compound from its name. We must also know how to state the
name of compound from it’s formula.
What would be the name of the ionic compound MgCl2?
write the name of the metallic element first
magnesium chloride
ide
write the name of the non-metallic element
but change its ending to “ide”

15. Calculating Formula Mass
We know that the average atomic mass of a single atom is given
on the Periodic Table for each element.
What would be the formula mass of
the ionic compound MgCl2?
The formula mass is the total mass of all the atoms in a single
formula unit . The formula unit is given by the chemical formula.
Using data from your periodic tables
for MgCl2
one Mg atom two Cl atoms
( 24.3) + (2 x 35.5) = 95.3

16. Calculating Formula Mass
Practice:
18.0
677.6
180.0

17. Ionic Compounds Containing Metals not in Group I, II or II
Recall Group I metals form +1 ions
Group II metals form +2 ions
Group III metals form +3 ions
the transition metals and some others
are interesting because they can have
+1
more than one ionic charge
+2 +3
iron for example can form
both Fe2+ and Fe3+ions
Fe

18. Ionic Compounds Containing Metals not in Group I, II or II
Since iron can form both +2 and +3 ions, there are two possible
chemical formulas for iron oxide. What would they be?
FeO iron II oxide
and and
Fe2O3 iron III oxide
Calling both compounds “iron oxide”
would be confusing. Different names
are required. Can you see from the
examples how these compounds were
named?

19. Ionic Compounds Containing Metals not in Group I, II or II
FeO iron II oxide
and and
Fe2O3 iron III oxide
III
IF a metal atom can form more +3
than one possible ion, a ROMAN
NUMERAL indicates the ionic
charge. +2
If the metal can only form one
possible ion (Group I, II, III, Zn
and Ag) then a roman numeral is +1
NOT included.

20. Try naming these compounds
BeCl2 beryllium chloride
CuBr2 copper II bromide
SnO2 tin IV oxide
Pb3P2 lead II phosphide

21. Write the chemical formulas for these compounds
sodium sulfide Na2S
copper I oxide CuO
nickel III chloride NiCl3
iron III nitride FeN

22. Structure of Ionic Compounds
Ionic compounds are crystalline solids. Positive and
negative ions arrange themselves in regular geometric
patterns.
This crystal lattice
structure is held
together strongly by
the ionic bonds.
These strong forces
mean ionic compounds
are brittle and have
high melting points.

23. Crystals of sodium chloride are made of numerous Na+ and Cl-
ions. Each ion is attracted to all the oppositely charged
neighboring ions.

24. Most ionic compounds are soluble and dissolve in water to
form solutions

25. Solutions of ions are electrolytes. They conduct electricity
because the dissolved ions are free to move.