HI is hydrogen iodide, a compound. It's important to note that oxidation numbers are assigned to individual atoms within a compound, not to the compound as a whole.

Here's how to determine the oxidation numbers for H and I in HI:

* Hydrogen (H): Hydrogen usually has an oxidation number of +1, except in metal hydrides where it has a -1 oxidation number. In HI, hydrogen is bonded to a non-metal, so it has an oxidation number of +1.

* Iodine (I): Since the overall charge of HI is neutral, the oxidation number of iodine must balance the +1 charge of hydrogen. Therefore, iodine has an oxidation number of -1.

In summary:

* The oxidation number of H in HI is +1.

* The oxidation number of I in HI is -1.