1. Determine the Charges:
* Aluminum (Al) is in Group 3A (or 13) of the periodic table, so it forms a +3 ion (Al³⁺).
* Selenium (Se) is in Group 6A (or 16) of the periodic table, so it forms a -2 ion (Se²⁻).
2. Find the Least Common Multiple (LCM):
* The LCM of 3 and 2 is 6.
3. Determine the Subscripts:
* To achieve a +6 charge, you need two aluminum ions (2 x +3 = +6).
* To achieve a -6 charge, you need three selenium ions (3 x -2 = -6).
4. Write the Formula:
* The formula for the ionic compound is Al₂Se₃.
