Question

Density of Li atom is 0.53 g ${cm}^{-3}$. The edge length of Li is 3.5 $\stackrel{\circ }{A}$ Find out the number of Li atoms in an unit cell $(N_A=6.023\times {10}^{23})$

• A. 2
• B. 8
• C. 4
• D. 6

Answer 1

Answer: (A)

2

The number of Li atoms in a unit cell is 2.

The density of the atom is given by the expression

density=(Zm/N(a^3))

Here, Z is the number of atom in a unit cell, m is the molecular mass of the atom, N is the Avogadro's number, and a is edge length

Plugging the values in the above equation

0.53=

z=2

Therefore the number of atom in a unit cell of Li is 2.