# What does an elements column number tell you about the atomic structure?

Well, the Group number, $1 - 18$ gives the NUMBER of valence electrons....
And $\text{Group Number "-=" column number}$
For the second short Period, $L i$ to $A r$...the Group number tells you the number of valence electrons, we got $L i , Z = 3$, i.e. $\text{Group 1}$, we got ONE VALENCE electron....
we got $F , Z = 9$, i.e. $\text{Group VII}$, we got SEVEN VALENCE electrons....