Question

Give the formula of

(a) Phosphate ion

(b) Aluminium ion

(c) Hydroxide ion

Answer 1

Formula of phosphate ion:

1. A Phosphate ion contains one phosphorous $\mathbf{\left(}\mathbf{P}\mathbf{\right)}$ atom and four oxygen $\mathbf{\left(}\mathbf{O}\mathbf{\right)}$ atoms.
2. It has three units of negative charge.
3. Thus, the formula of Phosphate ion is ${\mathbf{PO}}_{\mathbf{4}}^{\mathbf{3}\mathbf{-}}$.

Formula of aluminium ion:

1. An aluminium ion contains one aluminium $\mathbf{\left(}\mathbf{Al}\mathbf{\right)}$ atom.
2. It has three units of positive charge.
3. Thus, the formula of aluminium ion is ${\mathbf{Al}}^{\mathbf{3}\mathbf{+}}$.

Formula of Hydroxide ion:

1. An Hydroxide ion contains one oxygen $\mathbf{\left(}\mathbf{O}\mathbf{\right)}$ atom and one hydrogen $\mathbf{\left(}\mathbf{H}\mathbf{\right)}$ atom.
2. It has one unit of negative charge.
3. Thus, the formula of hydroxide ion is ${\mathbf{OH}}^{\mathbf{-}}$.