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According to Bohr's model, the radius of a hydrogen-like species is r = n² * h² / (4 * pi² * m * Z * e²). The radius of the hydrogen atom (Z=1, n=1) is 0.53 angstrom. Find the radius of Li^(2+) (lithium fully stripped to one electron).

1. 1.27 A
2. 0.17 A
3. 0.57 A
4. 0.99 A

Correct answer: 0.17 A

Solution

Bohr radius scales as n²/Z. Li^(2+) has Z=3 and ground state n=1. Note: though this question is labeled Physics, it belongs to Chemistry/Atomic Structure.

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