Question

how find valancy in any atom

Answer 1

The valency of an atom is equal to the number of electrons in the outer shell if that number is four or less. Otherwise, the valency is equal to eight minus the number of electrons in the outer shell. Once you know the number of electrons, you can easily calculate the valency

Answer 2

to find the valency,  count the no. Of electrons in outermost shell. 
If it is less than 4 the no. Itself becomes valency
If it is more than 4 , subtract it by 8 which becomes the valency

For example 
Na -2 8 1  -less than 4 so valency =1
Cl - 2 8 7 - more than 4 = 8-7 = 1

HOPE IT'S CLEAR

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