Here's why:
* Calcium is in group 2 of the periodic table, meaning it has a +2 charge as a cation (Ca²⁺).
* Hydroxide is a polyatomic ion with a -1 charge (OH⁻).
To form a neutral compound, we need two hydroxide ions (2 x -1 = -2) to balance the +2 charge of the calcium ion. This gives us the formula Ca(OH)₂.
The compound is called calcium hydroxide.
