Question

Which of the following are polyatomic ions?

• A. ${N{H}_4}^{+}$
• B. ${S{O}_4}^{2-}$
• C. ${Mn{O}_4}^{-}$
• D. $C{l}^{-}$

Answer 1

Answer: (A), (B), (C)

The correct options are
A ${N{H}_4}^{+}$
B ${S{O}_4}^{2-}$
C ${Mn{O}_4}^{-}$

Polyatomic ions are those ions which contain atoms of more than one element.
$$\begin{array}{cc}\text{Ions}& \text{Constituent Atoms}\\ {N{H}_4}^{+}& \text{1 N, 4 H}\\ {S{O}_4}^{2-}& \text{1 S, 4 O}\\ {Mn{O}_4}^{-}& \text{1 Mn, 4 O}\\ C{l}^{-}& \text{1 Cl}\end{array}$$Hence, from the given options, the polyatomic ions are:
${N{H}_4}^{+}$, ${{\mathrm{SO}}_4}^{2-}$, ${Mn{O}_4}^{+}$