Question

Write the ground-state electron configurations of an atom of the elements shown. Do not use a noble gas core.

If it can be done, rewrite the electron configurations in Questions 47 and 49 with a neon or argon core.

47)Magnesium and nickel
49)Chromium and selenium (z=34)

Answer 1

Magnesium : 1s2 2s2 2p6 3s2 / [Ne] 3s2
Nickel : 1s2 2s2 2p6 3s2 3p6 4s2 3d8 / [Ar]4s2 3d8
Chromium : 1s2 2s2 2p6 3s2 3p6 4s2 3d4 / [Ar] 4s2 3d4
Selenium : 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4 / [Ar] 4s2 3d10 4p4

Answer 2

chromium is wrong: the d orbital fills differently

Magnesium : 1s2 2s2 2p6 3s2 / [Ne] 3s2
Nickel : 1s2 2s2 2p6 3s2 3p6 4s2 3d8 / [Ar]4s2 3d8
Chromium : 1s2 2s2 2p6 3s2 3p6 4s 3d5 / [Ar] 4s 3d5
Selenium : 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4 / [Ar] 4s2 3d10 4p4