Question

Which of the following ions is a polyatomic ion?

Answer 1

The correct answer is option $NH{{+} \atop {4}} \right.$.

The $NH{{+} \atop {4}} \right.$ is an ion made up of two atoms nitrogen and hydrogen.

The polyatomic ions are those ions, which are formed by the binding of the two or more elements, which has a charge and act as an ion. As all others are formed by a single atom, they are not polyatomic, only $NH{{+} \atop {4}} \right.$ is formed by two atoms, hence, it is an polyatomic ion.