Na and Mg crystallize in bcc and fcc type crystals respectively, then the number of atoms of Na and Mg present in the unit cell of their respective crystals is:
Answers
Explanation:
In a cubic cell, the total volume of an atom belongs to eight atoms, hence one unit cell has only 1/8 part of the corner atom.
Since, BCC unit cell has one atom at the center of the cube along with 8 atoms at corners of the cube,
therefore total atoms in BCC
= 1/8 (part of corner atom) x 8 (corners) + 1 (central atom)
= 1/8 x 8 + 1
= 2 atoms
An FCC unit cell has total six faces and each face has has one atom. But the facial atom is always divided between two unit cells, henceforth only half part of facial atom belongs to one unit cell.
From above discussion, it is clear that the number of atoms in FCC cell
= 1/8 (part of corner atom) x 8 (corners) + 1/2 (part of facial atom) x 6 (no. of faces)
= 1/8 x 8 + 3
= 4 atoms
Hii hope this one helps you