The Correct Answer and Explanation is:
Correct Answer: Mg²⁺ and I⁻
When magnesium iodide (MgI₂), an ionic compound, is placed in water, it dissociates into its constituent ions. This process occurs because MgI₂ is formed from a metal (magnesium) and a nonmetal (iodine) through the transfer of electrons, creating positively and negatively charged particles.
Magnesium (Mg) is an alkaline earth metal located in Group 2 of the periodic table. Elements in this group characteristically lose their two valence electrons to achieve a stable electron configuration, similar to that of a noble gas. By losing two electrons, a magnesium atom becomes a magnesium cation with a positive two charge, which is represented as Mg²⁺.
Iodine (I) is a halogen in Group 17. Halogens are highly electronegative and tend to gain one electron to complete their outer electron shell, also achieving a stable configuration. When an iodine atom gains an electron, it becomes a negatively charged anion called the iodide ion, written as I⁻.
The chemical formula MgI₂ itself provides a clue to the ions formed. To create an electrically neutral compound, the total positive charge must balance the total negative charge. The +2 charge of a single magnesium ion (Mg²⁺) is balanced by the charge from two iodide ions, each with a -1 charge (2 x -1 = -2).
When MgI₂ dissolves in water, the polar water molecules surround the individual ions. The positive ends of water molecules are attracted to the negative iodide ions (I⁻), and the negative ends of water molecules are attracted to the positive magnesium ions (Mg²⁺). This interaction, called hydration, is strong enough to pull the ions apart from the solid crystal lattice, allowing them to move freely within the solution. The chemical equation for this dissociation is:
MgI₂(s) → Mg²⁺(aq) + 2I⁻(aq)
Thus, the ions formed are the magnesium cation (Mg²⁺) and the iodide anion (I⁻).
