1. Assign known oxidation states:

* H (hydrogen) has an oxidation state of +1 in most compounds.

* O (oxygen) has an oxidation state of -2 in most compounds (except in peroxides).

2. Set up an equation:

Let the oxidation state of Cl be represented by "x". The sum of the oxidation states in a neutral molecule must equal zero.

(+1) + (x) + 2(-2) = 0

3. Solve for x:

1 + x - 4 = 0

x = +3

Therefore, the oxidation state of Cl in HClO₂ is +3.