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The angular momentum of an electron in the 2nd Bohr orbit of hydrogen atom is x. What is the angular momentum of the electron in the first excited state of Li²+?

1. 3x
2. 9x
3. x/2
4. x

Correct answer: x

Solution

In Bohr's model, angular momentum L = n*h/(2*pi). For H atom at n = 2, L = 2*h/(2*pi) = x. The first excited state of any hydrogen-like ion is n = 2, so Li²+ at n = 2 also gives L = 2*h/(2*pi) = x.

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