Q1(d). Atoms in a BCC sample

Answer in brief

The sample contains 1.21×10²⁴ atoms.

Key points

• A conventional bcc cell contains two atoms. Its edge is 2.88×10⁻⁸ cm, so cell volume is 2.3888×10⁻²³ cm³.
• The sample volume is 104/7.20=14.444 cm³. Number of cells is sample volume divided by cell volume.
• Hence N=2(104)/(7.20(2.88×10⁻⁸)³)=1.2094×10²⁴. Equivalently the density data imply molar mass about 51.79 g mol⁻¹, which gives the same count.