Question

Which of the following is a polyatomic cation?

• A.
  Sulphate ion
• B.
  Carbonate ion
• C.
  Ammonium ion
• D.
  Dichromate ion

Answer 1

The correct option is C

Ammonium ion
The formulae of the given ions are mentioned below.

$\begin{array}{cc}\text{Ion}& \text{Formula}\\ \text{Sulphate ion}& S{O}_4^{2-}\\ & \\ \text{Carbonate ion}& C{O}_3^{2-}\\ & \\ \text{Ammonium ion}& N{H}_4^{+}\\ & \\ \text{Dichromate ion}& C{r}_2{O}_7^{2-}\end{array}$

Ammonium ion is a polyatomic cation because it contains a positive charge.

Hence, the correct answer is option (c).