Question

A metallic crystal crystallizes into a lattice containing a sequence of layers AB AB AB.... . Any packing of spheres leaves out voids in the lattice. What percentage of the volume of this lattice is empty space?

• A. $74\%$
• B. $26\%$
• C. $50\%$
• D. $33\%$

Answer 1

The correct option is B $26\%$

AB AB AB describes the hexagonal close-packed arrangement of spheres.

The available space occupied by spheres of equal size in three dimensions in the hexagonal close packed arrangement is 74%.

The vacant space is $100-74=26$%.

Hence, the correct option is $\text{B}$