Question

A solid is made of two elements A and B. Atoms of element A occupy all the tetrahedral sites while atoms of element B are in ccp arrangement. From this data find the formula of the compound. 

Answer 1

There are 2 tetrahedral sites per atom of B because atoms of element B have ccp arrangement. There are 2 atoms of element A for each atom of element B because all tetrahedral sites are occupied by atoms of element A. Therefore, the formula of the compound is A₂B.