Question

What is valency? Please explain

Answer 1

Valency is the combing capacity of an element .

for example valency of hydrogen is 1

valency is determined by number of valence electrons in the outermost shell

Answer 2

the combining capacity of  an element is called valency 

ATOMIC NO OF NITROGEN IS 7 

K shell =2 
L shell  =5

it requires 3 more electrons to obtain its octet

so the valency of nitrogen is -3