Co are Z(numar de ordine= nr.electroni)= 27---> 1atom are 27 e
1mol Co are masa atomica molara A=59g/mol
deci 59g contin 6,023x10²³ atomi(numarul lui Avogadro )
265,5g..................................N= 27X10²³atomi
1atom............27 e
27x10²³at.........x=732x10²³ e