Question

How to find valance electron group no. And period no. When electronic configuration is given

Answer 1

For example the electronic configuration of an element is 2 ,8 ,1
The number valence electron will be the no. of electrons in the outermost shell that is 1 . Period number will be the number of shells in the atom that is 3

Answer 2

Look here example

Oxygen=atmic no 8

Electronic configuration

=2,6

It need 2electrons to fill its electrnic configuration so its valency is 2

Another ex

Lithium atmic no=3

Electronic configuration

2,1

The outermost shell need to give one electron to balance its electronic configuration.and if here is 8 electrons so no need to give the electrons to other elements because outermost shell is fill but lithium needs to give one electron to the other element so its valency is 1

Here we go,