how to find valency of any element?
Answers
Valency
Valency refers to the capibility of sharing electrongs for an element while taking part in a chemical reactions.
In order to know valency of any element upto 18 atomic number we can use electronic configuration methods and the Bohr's rule of 2n^2.
According to 2n^2 rule,
Energy level of K shell = 2(1)^2 = 2
L shell = 2(2)^2 = 8
M shell = 2(3)^2 = 18
N shell = 2(4)^2 = 36
However outermost shell can only have 8 valence electrons and inner outermost shell can have 18 electrons
Taking example of Argon :
Atomic number of Argon = no. of electrons = 18
K shell = 2
L shell = 8
N shell ( outermost shell ) = 8
[ 2 + 8 + 8 = 18 ]
So Argon's all shells are completly filled so it can't react therefore will be counted as Noble gas.
Taking example of Oxygen :
Atomic no. = No. of electrons = 8
K shell = 2
L shell (outer most shell ) = 6
But it need 2 more lectrons to fill its outermost shell.
So valency of Oxygen is - 2.