# (solved)Question 2.31 of NCERT Class XI Chemistry Chapter 2

How many electrons in an atom may have the following quantum numbers? (a) n = 4, ms = - ½ (b) n = 3, l = 0

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### Question 2.31NCERT Class XI Chemistry

How many electrons in an atom may have the following quantum numbers? (a) n = 4, ms = - ½ (b) n = 3, l = 0

Note: Q 2.26, 2.27, 2.28, 2.29 and 2.30 are simple enough. So they have been skipped. Please write an email to us if you face any difficulty with any of them.

### Solution in Detail(video solution below this)

$\displaystyle \underline{\underline{\text{Part (a)}}}$

Total orbitals = $\displaystyle n^2$

Given: n = 4

$\displaystyle \therefore \text{ orbitals } = 4^2 = 16$

but each orbital can contain only one electron of spin -½

$\displaystyle \therefore$ total electrons $\displaystyle = 16\:\underline{Ans}$

$\displaystyle \underline{\underline{\text{Part (b)}}}$

Given n = 3, l = 0

but l = 0 means sub-shell = s

$\displaystyle \therefore$ orbital is 3s

but subshell s can have max. 2 electrons

$\displaystyle \therefore 2 \:\underline{Ans}$

### Video Explanation

Please watch this youtube video for a quick explanation of the solution: