1. Z=9.........> 9protoni
A=19---> 19=p+n---> neutroni= 10
2. Z= 10+2=20===> Ca 1s2 2s2 2p6 3s23p6 4s2---> per.4,gr.IIA
sunt 6 substraturi si 0 orbital monoelectronici
3. S+2e-------> S²⁻ Valenta 2-
dar si S-6e----> S⁺⁶ valenta 6+
4. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5 Z= 53
Fiecare substrat p are cate 3 orbitali p, deci sunt 12 orbitali p
Fiecare substrat d are cate 5 orbitali d, deci sunt 10 orbitali d
5--vezi in manual definitiile !!
