- Valency of ion is equal to the charge of the ions.
- Cations carry positive charge whereas Anions carry negative charge.
- When the valency is 1 for cations, they are called as Monovalent Cations.
- When the valency is 2 for the cations, they are called as divalent cations.
- When valency is 3 for the cations, they are called as Trivalent Cations.
| MONOVALENT CATIONS | DIVALENT CATIONS | TRIVALENT CATIONS |
| Hydrogen ion, H⁺ | Barium ion, Ba²⁺ | Aluminium Ion, Al³⁺ |
| Potassium ion, K⁺ | Calcium ion, Ca²⁺ | Iron ion, Fe³⁺ |
As anions have negative charge, the valency will be called as monovalent anion (1 ˉ), divalent anion (2ˉ) and trivalent anion as (3ˉ)
| MONOVALENT ANION | DIVALENT ANION | TRIVALENT ANION |
| Bromide ion, Brˉ | Sulphide ion, S²ˉ | Phosphide ion, P³ˉ |
| Nitrate ion, NO3ˉ | Sulphate ion, SO4²ˉ | Phosphate ion, PO4³ˉ |
To write the formula of a compound, following points need to be understood,
- Write the symbol of the element.
- Write the valency of the element below the symbol.
- Make a cross over the valency and the symbol & thus the desired formula will be the result.
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