Question

How many electrons are present in the M shell of an atom of an element with atomic number 24?

Please explain how to find.

Answer 1

If you normally write the electronic configuration of element with atomic number 24, the configuration is

1s2 2s2 2p6 3s2 3p6 4s2 3d4

K shell contains 1s

L shell contains 2s 2p

M shell contains 3s 3p 3d

So the number of electrons if we bluntly follow the configuration is 2+6+4 = 12

24 Cr chromium : [Ar] 3d⁵ 4s¹

1s2

2s2

2p6

3s2

3p6

3d5

4s1

2

8

13

1

K L M N
so the 3s² have 2 electrons , 3p⁶ have 6 electrons and 3d⁵ have 5 electrons
so the total number of electrons is 2+6+5=13 electrons in M shell

So the electrons in M shell is 2+6+5 = 13.

It's same as the manganese electronic configuration.