Question

how is the valency of an atom related to it's electronic configuration ​

Answer 1

Through the no. Of valence electrons v can calculate valency

Answer 2

If the valence electrons in the outermost shell is 1,2,3 then their valency is 1,2,3 resp. However if the electrons in the outermost shell are 5,6,7 then their valency is 3,2,1 resp

Hope this helps :)