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Sodium metal forms a body-centred cubic crystal lattice. If the edge length of its unit cell is 4.29 Å, the approximate atomic radius of sodium is:

1. 5.72 Å
2. 0.93 Å
3. 1.86 Å
4. 3.22 Å

Correct answer: 1.86 Å

Solution

In a body-centered cubic (BCC) structure, the relationship between the atomic radius (r) and the edge length (a) is given by the formula a = 4r/√3. By substituting the edge length of 4.29 Å into this formula and solving for r, we find that the atomic radius of sodium is approximately 1.86 Å.

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