4.2 – Ionic and Covalent Compound Naming
Ionic Compounds:
Salt, NaCl
- are made up of positive and negative
ions arranged in a crystal structure.
(metal and non-metal)
Covalent Molecules:
- are made up of atoms sharing
electrons.
Water, H2O
(non-metal and non-metal)
Naming Ionic Compounds:
 name
of an ionic compound = positive ion negative ion-ide
 Ex.1: magnesium and oxygen
 positive
ion negative ion-ide
 Magnesium ox + ide
 Magnesium oxide
 Ex.2:
what is the name of Ca3N2?
Ca = calcium; N = nitrogen
 Drop the end of the negative ion and add –ide
 Calcium nitride

 Ex.3:
What is the name of BaCl2?
 Barium
chloride
Magnesium oxide
is used as a
drying agent.
Writing formulas for Ionic Compounds
Remember: positive charges must = negative charges
Ex.1: What is the formula for magnesium phosphide?
 Magnesium is Mg2+ Phosphorous is P3–
 Lowest common multiple of 2 and 3 is 6
 3 Mg2+ ions & 2 P3– ions (6 +ve’s & 6 –ve’s)
 Magnesium phosphide = Mg3P2
Ex.2: What is the formula for calcium oxide?
Calcium is Ca2+
Oxygen is O2–
1 Ca2+ ion
&
1 O2– ion
Calcium oxide = CaO
Drawing Formula Diagrams

More Examples:
 Lithium
nitride
 Barium sulphide
Ionic Compound with a Multivalent Metal

Multivalent: some transition metals have more than
one charge.
 Roman
numerals are used after the metal name to
indicate which ion was used
Ex. 1 What is the formula manganese(III) sulphide?
 This manganese is Mn3+ Sulphur is S2–
 Lowest common multiple of 3 and 2 is 6
 2 Mn3+ ions and 3 S2– ions
 Mn2S3
You try!
What is the name for TiF4?
can be Ti4+ or Ti3+
Fluorine is F–
 From the ratio in the formula you can find out it is Ti4+
 1 Ti4+ ion and 4 F– ions
 Titanium (IV) fluoride
 Titanium
Polyatomic Ions

are made up of several atoms joined together by
covalent bonds
 The
whole group has a + or – charge, not individual
atoms.

Ex.1 What is the formula of sodium sulphate?
Na+ and SO42–
Na2SO4
Ex.2: What is the name of the compound KClO?
K+ = potassium
ClO– = hypochlorite
Potassium hypochlorite
Ex.3: What is the formula for Calcium nitrate?
Ca2+
and
NO3-
Ca(NO3)2
* Note the brackets around NO3 show there are two of
the nitrate ions present
Naming Simple Covalent Compounds

Prefixes are used before the atom name to indicate
the number of atoms in the molecule.
 Examples:
CO = carbon monoxide
CO2 = carbon dioxide
Write the most metallic atom (furthest
left) first, then add -ide to the end of
the second atom’s name
Examples:

What is the name of the molecule Si3P6?
 Trisilicon

hexaphosphide
What is the chemical formula for the molecule
trinitrogen tetrachloride?
 N3Cl4
How do you know which type it is?

To determine whether a compound is ionic or covalent:
- Examine the formula
•
•
Ionic compounds start with a metal or the ammonium ion
Covalent compounds start with a non-metal
Take the Section 4.2 Quiz