Question

The relationship between atomic radius (r) and lattice parameters (a) for a simple cubic (SC) structure is

• A. a = 2r
• B. a = 4r
• C. a = r/2
• D. a = r

Hint:

In simple cubic (SC) structures, atoms only touch along the cube edges. This makes a = 2r. SC structures are rare in nature because their packing efficiency is very low (approximately 52%), meaning most of the space in the unit cell is empty.

Answer 1

The Correct Option is A

In a simple cubic structure, the atoms are arranged such that the lattice parameter (a) is directly equal to twice the atomic radius (r), as the atoms touch each other along the edge of the unit cell. Therefore:
a = 2r