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Sodium metal crystallizes in a body centred cubic lattice with a unit cell edge of 4.29 Å. The radius of sodium atom is approximately:

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

Correct answer: 1.86 Å

Solution

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

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