The formula for the ionic compound formed from aluminum and selenium is Al₂Se₃.
The compound is formed by the transfer of electrons from aluminum to selenium, resulting in the formation of positively charged Al³⁺ ions and negatively charged Se²⁻ ions. The number of atoms in the resulting compound is determined by the need to balance the charges of the ions. Since aluminum has a +3 charge and selenium has a -2 charge, two aluminum atoms, and three selenium atoms combine to form Al₂Se₃.
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