Question

nitrogen( at. No.7) and phosphorus ( at. No.15) belong to group 15 of periodic table.write the electronic configuration of these two elemants and decide which of these two elements will be more electronegative and why?

Answer 1

Nitrogen (with atomic no.7). Atomic number is equal to number of protons in a neutral atom.
So using atomic no. we can write electronic configuration.
Electronic configuration of N = 2, 5
Since in first shell only 2 electrons can be filled, therefore rest 5 are filled in second shell.
Similarly we can do for Phosphorus, its electronic configuration = 2, 8, 5.

ELECTRONEGATIVITY: It is a tendency of a atom to gain electron.
Out of Nitrogen and Phosphorus, Nitrogen is electronegative atom, infact it is third most electronegative atom after Fluorine and Oxygen.
Reason:
As we go down in group, one more shell is added to the atom at every step due to which the size of atom increases.
As the size of the atom increases , its nucleus goes more deep inside the atom. Therefore, the attraction of nucleus for the incoming electron decreases, due to which the atom can not form negative ions easily and electronegative character decreases.