Question

Choose the electron configurations which are impossible for an unexcited atom.

Example 1 – 1s22s22p4


Example 2 – 1s22s22p63s23p33d1


Example 3 – 1s22s22p83s1


Example 4 – 1s22s22p63s1

Answer 1

Example 2 and Example 3.

In example 2, one electron from 3p went to 3d. 3p needs to be filled up first will electrons in order for 3d to start filling up.

In example 3, one electron from 3s and 3p went to 2p. 2p can only hold 6 electrons not 8.