Question

How many electrons in an atom may have the following quantum numbers?

1. n = 4, ms = – $\frac 12$
2. n = 3, l = 0

Answer 1

(a) Total number of electrons in an atom for a value of n = 2n2
∴ For n = 4,
Total number of electrons = 2(4)2 = 32
The given element has a fully filled orbital as
$1s^2 \ 2s^2\ 2p^6\ 3s^2\ 3p^6\ 4s^2\ 3d^{10}$.
Hence, all the electrons are paired.
∴ Number of electrons (having n = 4 and ms = $-\frac 12$) = 16

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(b) n = 3, l = 0 indicates that the electrons are present in the 3s orbital.
Therefore, the number of electrons having n = 3 and l = 0 is 2.