CBSE Class 10 Science 2020 · Paper 31/3/1 · Question 25(b)

(i) Magnesium ($2,8,2$) loses its two outermost electrons, one to each of two chlorine atoms ($2,8,7$): $\text{Mg}⟶{\text{Mg}}^{2+}+2e^{-}$ and $\text{Cl}+e^{-}⟶{\text{Cl}}^{-}$, so $\text{Mg}+2\text{Cl}⟶{\text{Mg}}^{2+}+2{\text{Cl}}^{-}$, that is, ${\text{MgCl}}_2$. The ions present are the magnesium ion ${\text{Mg}}^{2+}$ (cation) and the chloride ion ${\text{Cl}}^{-}$ (anion). (ii) In ionic compounds very strong forces of attraction exist between the positive and negative ions; they hold the ions firmly in place, so ionic compounds are solids (and somewhat hard, with high melting points). (iii) Labelled diagram: glass wool soaked in water and the metal sample in a boiling tube clamped on a stand and heated with a burner; a delivery tube through the cork leads under water in a trough into an inverted test tube, in which the hydrogen gas formed collects (for example, $3\text{Fe}+4{\text{H}}_2\text{O}⟶{\text{Fe}}_3{\text{O}}_4+4{\text{H}}_2$).