Final answer:
Two chloride ions are needed to stabilize the 2+ charge of a single magnesium ion, forming the ionic compound magnesium chloride with the formula MgCl₂.
Step-by-step explanation:
The question addresses the formation of magnesium chloride, an ionic compound composed of magnesium ions (Mg₂+) and chloride ions (Cl⁻). To stabilize the 2+ charge of a magnesium ion, two chloride ions, each with a 1- charge, are required. This charge balancing results in the chemical formula MgCl₂, indicating two chloride ions for every magnesium ion, reflecting a 1:2 ratio.