Give a reason why - in the formation of electrovalent compound - magnesium chloride, one magnesium atom combines with two chlorine atoms to give magnesium chloride. [at. no. Mg=12, Cl=17, ]

Magnesium [At. no. 12 and electronic configuration 2,8,2] loses two electrons from it's outer shell in order to attain stability of nearest noble gas Neon [2,8] and becomes a magnesium ion [cation] : Mg²⁺.

Chlorine [At. no. 17 and electronic configuration 2,8,7] accepts one electron in it's outer shell to attain stability of nearest noble gas Argon [2,8,8] and becomes a chloride ion [anion] : Cl^1-.

Magnesium atom donates two electrons, whereas chlorine accepts one electron to give - chloride ion. Therefore, to accept the other electron donated by magnesium atom there must be another chlorine atom. Thus, one magnesium atom combines with two chlorine atoms to give MgCl₂