Answer :
The edge length of the NaCl unit cell can be derived as twice the sum of the radii of Na⁺ and Cl⁻, which totals 552 pm, hence correct answer is D) 552
To calculate the edge length of the unit cell in NaCl, we first need to acknowledge that NaCl crystallizes in a face-centered cubic (FCC) structure. In an FCC lattice, each edge of the unit cell consists of the anion-cation-anion sequence without any gap.
This means that the edge length is twice the radius of the anion plus twice the radius of the cation. Consequently, for NaCl, the edge length (a) can be calculated as follows:
- a = 2(radius of Na⁺) + 2(radius of Cl⁻)
- a = 2(95 pm) + 2(181 pm)
- a = 190 pm + 362 pm
- a = 552 pm
Therefore, the correct answer is D. 552 pm.
