Q. An orbital electron in the ground state of hydrogen has an angular momentum $L_{1}$, and an orbital electron in the first orbit in the ground state of lithium (double ionised positively) has an angular momentum $L_{2}$. Then :

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A

$L_{1}=L_{2}$

B

$L_{1}=3 L_{2}$

C

$L_{2}=3 L_{1}$

D

$L_{2}=9 L_{1}$

Solution:

Doubly ionised positively lithium ion is a hydrogen like atom so we use
$L=m v r=\frac{n h}{2 \pi}$
Also for both $n=1$ we have
$L_{1}=L_{2}=\frac{h}{2 \pi}$

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