Q50 / 150 · MHT CET 2026 (20 April Shift 1) · Chemistry

Calculate the radius of atom of metal forming fcc unit cell having edge length $360$ pm

  • A
    $180.04$ pm
  • Correct answer
    B
    $127.26$ pm
  • C
    $155.91$ pm
  • D
    $254.67$ pm

Solution

For a face-centered cubic (fcc) unit cell, the atoms touch each other along the face diagonal.

The relationship between the edge length $a$ and the atomic radius $r$ is given by:

$\sqrt{2}a = 4r$

$r = \dfrac{a}{2\sqrt{2}}$

Given $a = 360$ pm:

$r = \dfrac{360}{2\sqrt{2}} = 90\sqrt{2}$

Using $\sqrt{2} = 1.414$:

$r = 90 \times 1.414 = 127.26$ pm

Answer: $127.26$ pm

Hence, the correct answer is option: 'B'.

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