z=19K
1s2/2s2 2p6/3s2 3p6/4s1
4 straturi si 6 substraturi
z=21Sc
1s2/2s2 2p6/3s2 3p6/4s2 3d1
4 straturi si 7 substraturi
z=29 Cu
1s2/2s2 2p6/3s2 3p6/4s1 3d10
4 straturi si 7 substraturi
z=33As
1s2/2s2 2p6/3s2 3p6/4s2 3d10 4p3
4 straturi si 8 substraturi
elementele care au un singur orbital monoelectronic sunt: K; Sc; As
Atomul de As are cel mai mare numar de electroni necuplati