Question

which of the following may have same set of quantum numbers?ans is last electron of Sc and last electron of Fe, How?

Answer 1

Dear student

The atomic number of Sc is 21. It's electronic configuration can be written as:

1s² 2s² 2p⁶ 3s² 3p⁶ 4s^{2 ​} 3d¹ (According to Aufbau's principle 4s will be filled first and then 3d will be filled)

The 21^st electron of Sc will reside in 3d orbital. The quantum numbers can be given as:

n=3

l=2 (d)

m=-2

s=+1/2 (upward spin)

ii) The last electron of Fe is 3d⁶4s²
will reside in the 3d orbital. The quantum numbers are
n=3

l=2 (d)

m=-2

s=+1/2 (upward spin)

Regards