Explain how you use the periodic table to tell you that there are two chloride ions for every magnesium ion in magnesium chloride (MgCl2) and one chloride ion for every sodium ion in sodium chloride (NaCl).

Magnesium is present in group two while sodium is present in group one. The magnesium atom have two valance electrons while sodium have one.

The chlorine is present in group seventeen and it have seven valance electron. To complete the octet chlorine atom needed one electron. magnesium lose its two electron to complete the octet and sodium lose its one valance electron. So,

When magnesium is combine with chlorine it loses its two electrons. The electrons are accepted by the two atoms of chlorine.

Mg²⁺ and 2Cl⁻

MgCl₂

When sodium is combine with chlorine atom it lose its one electron which is accepted by one chlorine atom.

Na⁺ Cl⁻

NaCl