The formula for copper(II) chlorate is Cu(ClO₃)₂. Here's how we arrive at that:

* Copper(II) indicates the copper ion has a +2 charge (Cu²⁺).

* Chlorate is the polyatomic ion ClO₃⁻ with a -1 charge.

To balance the charges, we need two chlorate ions (2 x -1 = -2) to match the +2 charge of the copper ion. Therefore, the formula becomes Cu(ClO₃)₂.