Compounds can be named by using common names or standard names as proposed by International Union for Pure and Applied Chemistry (IUPAC).
BINARY COMPOUNDS
Binary compounds are the compounds consist of two elements (but not necessarily two atoms).
Naming Binary Ionic Compounds
Binary ionic compounds contain a metal as a positive ion and a non-metal as a negative ion.
RULES FOR NAMING BINARY IONIC COMPOUNDS
The name starts with the metal and ends with a non-metal.
The name of metallic ion is the name of element itself.
The name of non-metal which form the second part of the name ends up with the suffix “-ide”.
Examples,
Oxygen→ oxide
Fluorine→ fluoride
Sulphur →sulphide
Bromine→ bromide
Nitrogen→ nitride
Chlorine→ chloride
Hydrogen →hydride
Examples
Name the following compounds
CaCl2 Calcium chloride
Mg3N2 Magnesium nitride
Al2O3 Aluminium oxide
Naming binary ionic compound containing metal with variable oxidation states.
For metals with variable oxidation states, their names should indicate the oxidation state a given metal has used in forming such compound.
The name of the metal exhibiting variable oxidation state is followed by the oxidation number written by using roman numerals and enclosed in the brackets.
Examples
Name the following compounds
CuCl2 copper(II) chloride.
PbCl2 lead (II) chloride.
Hg2Cl2 mercury (I) chloride
HgCl2 mercury (II) chloride
CuO copper (II) oxide
Cu2S copper (I) sulphide.
Name the following compounds
CaO
PbCl4
FeCl3
Fe2O3
AlN
Naming ionic compounds containing Radicals
A radical is the group of atoms that act as one atom but does not exist independently.
With exception to ammonium ion (NH4+ ) most radicals are negatively charged.
In naming these, you start with a metal or positive ion and end up with the name of the radical as discussed in radical section.
Examples
CaSO4 calcium sulphate
Na3PO4 sodium phosphate.
NaHCO3 sodium hydrogencarbonate
CaCO3 calcium carbonate.
NaOH Sodium hydroxide
Naming Binary Covalent Compounds.
Binary covalent compounds are compounds with two elements usually non-metals.
Rules for naming covalent compounds
The name of the first element is the name of element itself.
The name of the second element ends up with suffix “-ide”.
Sometimes the number of atoms of each element is indicated by using the following prefixes
Number of atoms
Prefix
Prefix used
1
Mono-
Mono-
2
Di-
Di-
3
Tri-
Tri-
4
Tetra-
Tetr-
5
Penta-
Pent-
6
Hexa -
Hex-
7
Hepta -
Hept-
8
Octa -
Oct-
9
Nona -
Non-
10
Deca-
Dec-
Note:
We sometimes omit some parts of the word in the prefixes wehen naming some elements which start with vowels such as oxide. For example tetroxide instead of tetraoxide. But for consonants we use use as indicated "eg. tetrachloride and not tetrchloride"
Example
Name the following compounds
CO carbon monoxide.
SF6 sulphur hexafluoride
PCl3 phosphorus trichloride
Special Cases
Some compounds use common names.
Examples
Chemical formula
Common name
Names of covalent compound
NH3
ammonia
nitrogen trihydride
H2O
water
dihydrogen monoxide
PH3
phosphine
phosphorus trihydride.
Like metals, most non-metals exhibit variable valencies. Their IUPAC names should therefore include the valency of that element in a compound.
→In this case, the oxidation state of the first element should be calculated and included in the name of the compound. The second non-metal should end up with the suffix “-ide” without stating the number of atoms present.
Example
CO the oxidation state of carbon is +2 the name of this compound is Carbon (II) oxide.
CO2 Carbon (IV) oxide.
PCl5 Phosphorus (V) chloride.
Practice
Name the following chemical compounds
SO2
SO3
P4O10
SiF6
Name these compounds by using IUPAC system
SO2
P4O10
Naming acids
Names of most acids end up with the suffix “-ic”.
In systematic naming oxy-acids, the oxidation state of the non-oxygen element other than hydrogen must be indicated.