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If the radius of the 3rd Bohr orbit of hydrogen is x, what is the radius of the 4th Bohr orbit of the Li²+ ion?

1. 27/16 x
2. 16/27 x
3. 9/16 x
4. None of these

Correct answer: 16/27 x

Solution

r3(H)=9a0 and r4(Li²+)=16a0/3, so r4(Li²+)/r3(H)=16/27, giving r4(Li²+)=16x/27.

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