* Know the oxidation states of common elements: Oxygen usually has an oxidation state of -2, and hydrogen usually has an oxidation state of +1.

* The sum of oxidation states in a neutral compound must equal zero.

Let's break down Mg(OH)₂:

* Oxygen (O): There are two oxygen atoms, each with an oxidation state of -2, contributing a total of -4.

* Hydrogen (H): There are two hydrogen atoms, each with an oxidation state of +1, contributing a total of +2.

* Magnesium (Mg): Let 'x' be the oxidation state of magnesium.

To find 'x', we set up the equation:

x + (+2) + (-4) = 0

Solving for 'x':

x - 2 = 0

x = +2

Therefore, the oxidation state of Mg in Mg(OH)₂ is +2.