Consider the following table:

Element	Atomic no.	No. of neutrons
A	3	4
B	9	10
C	13	14
D	17	18
E	18	22

The valency of E is:

• In chemistry, valence, sometimes called valency, is a characteristic of an element that establishes how many other atoms of the element each atom can interact with. 
• The element E given in the table has atomic number 18 which means its electronic configuration is as 2,8,8. which is Argon.
• This shows that the outermost shell has 8 electrons and it is a fully filled shell. Hence, the element E has a valency of 0. It is a noble gas and they have zero valency value.

Hence, the valency of E is 0.