Which of the following be the basis of entry of an electron is `4s` orbital before `3d` orbital ?

Options

A. Energy level diagram
B. Hund's rule
C. Pauli's principle
D. Screening effect

Answer

A

Explanation

`n + 1 of 4s` is `4 + 0 = 4` and that of `3d` is `3 + 2 = 5` Therefore the energy of `4s ` is lower than that of `3d`
Increasing order of energy
`1s lt 2s lt 2p lt 3s lt 4s lt 3d lt 4p lt 5s lt 4d lt 6s lt 4f lt 5dlt 6p lt 7s lt 5f lt 6d lt 7p`
The maximum number of electron that can be accommodate in s orbital is `2` in p orbital is `6` in d orbital is `10` and in f orbital is `14`