Naming chemical compounds from their fromula
Usually the elements present in a compound are named in order of symbols appearing in formula. Following rules are applied in a naming a compound.
Rule 1: If a compound contains only two elements (binary compounds) such that one of them is metal, the metal is named first.Non-metalic part is a given a suffix, ‘ide’ at the end.
Examples:
i)Compound of sodium and chlorine is sodium chloride (NaCl)
ii)Compound of magnesium and nitrogen is magnesium nitride (Mg3N2)
iii)Compound of calcium and sulphur is calcium sulphide (CaS)
Rule 2: The compound containing two non metals are named by using Greek prefix like mono, di, tri, tetra, penta, which denotes the number of atoms present in the compound.
Examples:
i) CO stands for carbon monoxide
ii) CO2 stands for carbon dioxide
iii) PCl5 stands for phosphorous pentachloride.
iv) SO3 stands for sulphur trioxide.
Rule 3:
Compounds containing three elements (tertiary compouds), one of which is oxygen, are named with suffix -ate at the end, provided there is only one such compoud. If there are two compounds, the one with more oxygen is named with suffix-ate ending and one with less oxygen is named with - ite ending compoud. If there are two compounds, the one with more oxygen is named with suffix-ate ending and one with less oxygen is named with - ite ending.
Examples:
i) a) NaNO3 Sodium nitrate b) NaNO2 Sodium nitrite
ii) a) CaSO4 Calcium sulphate b) CaSO3 Calcium sulphite
Rule 4: In a compound oxygen is less than the oxygen present in a compound. ending with- ite, then it is given the prefix hypo-in the beginning and if oxygen present in a compound ending with- ate is more, then it is given the prefix per- in the beginning
Examples:
i) “KClO is named potassium hypo-chlorite as it contains less oxygen than potassium chlorite KClO2
ii) KClO4 is named potassium per-chlorate as it contains more oxygen than potassium chlorate (KClO3)
Cl- (Chloride) ClO- (Hypo Chlorite)
ClO2- (Chlorite) ClO3- (Chlorate) ClO4- (Per Chlorate)