Question

an element X has mass number 4 and atomic number 2 write its electronic configuration of the number protons electrons and neutrons what is valency give reason

Answer 1

mass no = 4
p+n =4
2+n =4
neutrons =2
e.c =2
valency =0 as its outermost shell is filled

Answer 2

Here is ur ans....
electronic configuration:
0
no. of protons=2
,, ,, neutrons=2
,, ,, electrons=2
valency=0
Bcz the element has been completed its orbit..