Question

Thallium chloride (atomic mass $=240$ g mol${}^{-1}$) crystallises in either a simple cubic lattice or a face centered cubic lattice with chloride ions at the face-centres and $T{i}^{+}$ ions in the holes. If the density of the solid is $9.0$ g cm${}^{-3}$ and edge of the unit cell is $3.85\times {10}^{-8}$ cm, what is the unit geometry?

• A. HCP
• B. BCC
• C. FCC
• D. SC

Answer 1

The correct option is D SC

As we know, density $=\frac{n\times M}{V\times N_A}$, where n is the number of atoms per unit cell.

$9=\frac{n\times 240}{(3.85\times {10}^{-10}{)}^3\times (N_A)}$ $⟹n=1$

So, it is a simple cubic lattice.