Here's how to understand the formula:

* Bismuth (Bi): Bismuth is a metalloid with a charge of +3 in this compound.

* Tellurium (Te): Tellurium is a metalloid with a charge of -2 in this compound.

To balance the charges, you need two bismuth atoms (+6 total charge) and three tellurium atoms (-6 total charge). This gives you the formula Bi₂Te₃.