Diamond has a three dimensional structure of C atoms formed by covalent bonds. The structure of diamond has face centred cubic lattice where 50% of the tetrahedral voids are also occupied by carbon atoms. The number of carbon atoms present per unit cell of diamond is ____________.

KBr is doped with 10^$$-$$5 mole percent of SrBr₂. The number of cationic vacancies in 1g of KBr crystal is ____________ 10¹⁴. (Round off to the Nearest Integer).

[Atomic Mass : K : 39.1 u, Br : 79.9 u N_A = 6.023 $$\times$$ 10²³]

Ga (atomic mass 70 u) crystallizes in a hexagonal close packed structure. The total number of voids in 0.581 g of Ga is __________ $$\times$$ 10²¹. (Round off to the Nearest Integer). [Given : N_A = 6.023 $$\times$$ 10₂₃]

A certain element crystallises in a bcc lattice of unit cell edge length 27$$\mathop A\limits^o $$. If the same element under the same conditions crystallises in the fcc lattice, the edge length of the unit cel in $$\mathop A\limits^o $$ will be ____________. (Round off to the Nearest Integer).

[Assume each lattice point has a single atom]

[Assume $$\sqrt 3 $$ = 1.73, $$\sqrt 2 $$ = 1.41]