The correct formula for the compound formed when aqueous solutions of magnesium and chloride ions are mixed is MgCl₂. Here's why:

* Magnesium (Mg) is a Group 2 element, meaning it forms +2 cations (Mg²⁺).

* Chloride (Cl) is a Group 17 element, meaning it forms -1 anions (Cl⁻).

To form a neutral compound, we need two chloride ions (2 x -1 = -2) to balance the +2 charge of the magnesium ion. This gives us the formula MgCl₂.

The compound is called magnesium chloride.