JAMB Chemistry 2011 Paper

Concept:Elements with atomic numbers 12 and 17 are a metal and a non-metal, which form an ionic bond.Explanation:Element X has atomic number 12, so it is magnesium, $\mathrm{Mg}$, a metal with electron configuration $2,8,2$.Element Y has atomic number 17, so it is chlorine, $\mathrm{Cl}$, a non-metal with electron configuration $2,8,7$.Magnesium loses 2 electrons to form $\mathrm{Mg}^{2+}$, while each chlorine atom gains 1 electron to form $\mathrm{Cl}^{-}$.The bond formed by the transfer of electrons between a metal and a non-metal is an electrovalent (ionic) bond.Answer:A. Electrovalent