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Question
Aluminium crystallises in a cubic close-packed structure with a unit cell edge length of 353.6 pm. What is the radius of Al atom? How many unit cells are there in 1.00 cm3 of Al?
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Solution
Using the formula (i),
r = 0.3535 a
∴ r = 0.3535 × 353.6 = 125 pm
Using the formula (ii),
Number of unit cells in volume (V) of metal = `"V"/"a"^3`
∴ Number of unit cells in 1.00 cm3 of Al = `1.00/(3.536 xx 10^-8)^3`
= 2.26 × 1022
- Radius of Al atom (r) is 125 pm.
- Number of unit cells in 1.00 cm3 of Al is 2.26 × 1022.
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