An element crystallizes in a structure where its constituent atoms touch each other strictly along t — Solid State Chemistry Question

💡 Solution & Explanation

Atoms touching strictly along the body diagonal identifies a BCC unit cell. For BCC, $4r=\sqrt{3}a$ and $Z=2$. Packing efficiency $=\frac{2\cdot\frac43\pi r^3}{a^3}=\frac{\sqrt{3}\pi}{8}\approx0.68$, i.e. $68\%$.