Question

How do you determine valence electrons when given group number?

Answer 1

The Group number gives the number of valence electrons to a first approximation........

Explanation:

Consider the first few short periods.......

Hydrogen, Group 1, has the ONE valence electron.....

Helium, Group 18, has the TWO valence electrons.....and therefore has a complete valence shell, and is supremely unreactive.....

And for Period 2, `Li`, `Be`, `B`, `C`

Lithium, like hydrogen, is Group 1, and thus has the one valence electron. Beryllium, Group 2, has 2 valence electrons. Boron, Group 3 or Group 13, has 3 valence electrons, and carbon, Group 14, has 4 valence electrons.........Get the picture?

Anyway, do you have a copy of the Periodic Table in front of you? Its structure DIRECTLY reflects electronic structure.......