Question

A compound is formed by two elements M and N. The element N forms ccp and atoms of M occupy 1/3 rd of tetrahedral voids. What is the formula of the compound?

Answer 1

As the element N form ccp (cubic close packing), the atoms of N occupy face centres as well as corners.

The atoms of M occupy one-third of the 8 tetrahedral voids.

Effective number of 'N' atoms = (8 x 1/8) + (6 x 1/2) = 1 +3 = 4

Effective number of 'M' atoms = (1/3 x 8) = 8/3

Thus, the formula becomes M⁸/₃N₄

Multiplying with 3 in the subscript, we get the formula as

M₈N₁₂

Hope it helps!!

Answer 2

Hey there!

----------

Answer :

N forms ccp means number of N = 8 × $\frac{1}{8}$ = 1

M occupies $\frac{1}{3}rd$ of tetrahedral voids.

Total number of voids = 2 × N

⇒ Total number of M = 2 × $\frac{1}{3}$ = $\frac{2}{3}$

∴ M : N = $\frac{2}{3}$ : 1 = 2 : 3

Therefore, formula is $M_{2} N_{3}$