2 valence electrons
6
1
2 electrons in each shell: 2,8,18,18,8,2
Valences of einsteinium are 2, 3 and 4.
The valences of polonium are 2, 4 and 6.
Many elements have two or more valences.
Valences of polonium are: 2, 4, 6 and -2.
Technetium valences are between -1 and +7; the most usual valences are +3, +4 and +7.
Helium has one kind of atom: helium.
Berkelium has the valences 3+ and 4+.
Helium has 2 electrons.
Helium has 2 protons.