Plx answer is 7th question
Q.7. Find the valency of ${}_7{}^{17}N and {}_{17}{}^{35}Cl$

Dear Student 

Valency is the measure of the reactivity of the atom or the molecule. 
So, it only depends upon the number of protons or the number of electrons hence it does not change with isotope. 
So, the valency for nitrogen is 3. 
And the valency for chlorine is 1. 

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