1. Identify the Ions:
* Magnesium (Mg): Magnesium is a metal in Group 2 of the periodic table. It forms a +2 cation (Mg²⁺).
* Phosphite ion (PO₃³⁻): The phosphite ion has a -3 charge.
2. Balance the Charges:
To form a neutral compound, the positive and negative charges must balance. The least common multiple of 2 and 3 is 6.
* We need three magnesium ions (3 x +2 = +6)
* We need two phosphite ions (2 x -3 = -6)
3. Write the Formula:
The formula for the compound is Mg₃(PO₃)₂.
Therefore, the correct formula for the compound formed between magnesium and phosphite ion is Mg₃(PO₃)₂.
