Question

chemistry give answer

Answer 1

Valency oh H =1
And O=2

when You are going to calculate the formula of Hydrogen and oxygen
then the valency cross

then we get H2O

in which in each reaction the combin with 2 atom of H and 1 of O

Answer 2

The valency of H ( Hydrogen) is 1..n that of O( Oxygen ) is 2.
When they both combine the valencies are crossed ...
Therefore we get H2O.