Question

Correct the errors in the following? a) `1s^2 2s^3 2p^7` b) `1s^2 2s^2 3p^6 3s^2 3d^8` c) `1s^3 2s^2 2p^6 3s^2 3p^5 4s^1` d) `1s^1 2s^2 2p^6 3s^2 3p^6 3d^7`

Answer 1

the first one will be `1s^2 2s^2 2p^6 3s^2`, as

`2s` and `2p` orbital can each have a maximum of `2` electrons. We keep the same number of electrons, so we promote the two extra ones to the next orbital up.

2nd one will be `1s^2 2s^2 2p^6 3s^2 3p^6 3d^8`

(following normal energy ordering)

Next one will be `1s^2 2s^2 2p^6 3s^2 3p^6 4s^1`

(again following the Aufbau principle of filling the orbitals,you can't have one electron in `4s` without filling the vacant spaces in `3p`, and `1s` can have a maximum of `2` electrons)

And the last one `1s^2 2s^2 2p^6 3s^2 3p^6 3d^6`

(`1s` can accommodate a maximum of `2` electrons, which must be filled first before filling `2s`)