WAEC Chemistry 2013 Paper

Concept:When an atom gains electrons, it becomes negatively charged because the number of electrons exceeds the number of protons.The magnitude of the negative charge equals the number of electrons gained.Explanation:An atom of element $X$ is electrically neutral.It contains equal numbers of protons and electrons.When $X$ gains two electrons, the electron count becomes two more than the proton count.This excess of negative charge gives the atom a charge of $-2$.So, the symbol for the ion is $X$ with a superscript of $2-$.This means the ion carries a double negative charge.Among the given options, the correct representation is $X^{2-}$.Answer:$\mathrm{X}^{2-}$, i.e. option C.