posted by sushil .
what valency ?how can we find valency?explain.
a measure of its combining power with other atoms when it forms chemical compounds or molecules.
It's very easy and simple.
1st pt. No. of electrons in last shell should be 8
2Nd Use 2n*n where n is the no. of the shell K,L,M etc. this formula is used to find no. of electrons that can be accommodated in a shell
For ex if you want valency of element with atomic no.34
Then Using the formula
For 1st shell 2*1*1=2
For 2nd shell 2*2*2=8
For 3rd shell 2*3*3=18
Here's the trick adding the electrons in these shells.=28 And the no. left is 6
So as we know we need 8 electrons in last shell so, 2 electrons are less so the valency is -2
if the atomic no.were 36 it would be a noble gas valency=0, 37 then a valency =+1