Question

Write the electronic configuration of ${}_{19}{K}^{40}$.

• A. 2, 8, 9
• B. 2, 8, 8, 1
• C. 2, 8, 8, 3
• D. 2, 8, 18, 12

Answer 1

The correct option is A

2, 8, 9

Neil's Bohr proposed that each shell can accommodate a maximum of $2n^2$, where $n$ is the shell number.

The atomic number of potassium is 19 and the mass number is 40.
According to the Neil's Bohr out of the 19 electrons, K shell can accommodate 2 electrons, L shell can accommodate 8 electrons, M shell can accommodate 8 electrons and N shell had one electron in it.

Hence the electronic configuration of potassium is (2,8,8,1).