Copper
29
1s2 2s2 2p6 3s2 3p6 3d10 4s1
[Ar] 3d104s1
Chromium
24
1s2 2s2 2p6 3s2 3p6 3d5 4s1
[Ar] 3d5 4s1
Order of filling
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 5d10 7p6 8s2
Helium
2
1s2
Neon
10
2p6
Argon
18
3p6
Krypton
36
4p6
Xenon
54
5p6
Radon
86
6p6
Oganesson
118
7p66
Lithium
3
Sodium
11
Potassium
19
Rubidium
37
Caesium
55
Francium
87