Ga ( atomic mass 70m)crystallizes in a hexagonal close packed structure. The total number of voids in 0.581 g of Ga is ____________×1021 .(Round off to the Nearest Integer)

Ga Crystallizes as If number of Particles per unit cell = n ,  number. of Tetra hedron voids = 2n number. of octa hedron voids =   n,     Total = 3nno. of Ga particles given =WGAW×NA=0.58170×6.023×1023=0.0499×1023 atom For one particles – 3 voids        ∴0.0499×1023→?0.0499×10231×3=0.1499×1023 voids ∴14.99×1021≅15×1021 voids ∴X=15