1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1
1s
2
2s–2p
3
3s–3p
4
4s–3d–4p
5
5s–4d–5p
6
6s–4f–5d–6p
7
7s–5f–6d