How does the number of valence electrons change from left to right across the periodic table?

1 Answer


The number of valence electrons goes up by one each time you move another column (group) to the right.


There are a few things to look out though when trying to figure out the number of valence electrons.

Group 1 elements have one valence electrons, and Group 2 elements have 2 valence electrons. Groups 13-17 have 3,4,5,6 & 7 valence electrons respectively. The noble gases (group 18) have 8 valence electrons except for He which has only 2 valence electrons.

Elements in groups 3-12 are referred to as the transition metals and there are more exceptions to rules for determining valence electrons for these elements.

Here is a video review of Lewis structures and valence electrons.

Hope this helps!