Question

The valencies (or charges) of some of the ions are given below :

Ion            Valency        Ion                Valency                        (Charge)                             (Charge)

Sodium ion       1+      Nitrate ion            1–  
Copper ion       2+       Sulphide ion         2–

Using this information, write down the formulae of :

1. Sodium sulphide
2. Copper nitrate

Answer 1

Formula of the listed compounds can be derived by crossing the individual valencies over the ions/elements. Therefore, the formula for sodium sulphide and copper nitrate are:

1. Na₂S
2. Cu(NO₃)₂