How do you find the number of valence electrons in an atom?

1 Answer
Apr 22, 2018

Group number or using proton number.


Most of the time you can determine the number of valence electrons by the number of the group it is in. For example, #Na# is in Group #I# and hence it has one valence electron.

However it is not always conventional as transition metals does not technically have a group number. Thus we use its proton number. Since atoms are nuetrally charged, proton number = electrons in any atom. Thus, we can determine its electron number and write our its configuration. #Fe# has an electronic configuration of [Ar] 3d6 4s2 and thus 2 valence electrons.