Statement : The plot of atomic number ( y -axis ) versus number of neutrons ( x -axis ) for stable nuclei shows a curvature towards x-axis fron the line of ` 45^@` slope as the atomic number is increased .
Explanation : proton -proton electrostatic repulsions begin to overcome attracive forces involving protons and neutrons in heavier nuclides.

Options

A. If both (A) and (R ) are correct, and (R ) is the correct explanation of (A).
B. If both (A) and (R ) are correct, but (R ) is not the correct explanation of (A)
C. If (A) is correct, but (R ) is incorrect.
D. If (A) is incorrect, but (R ) is correct

Answer

A

Explanation

The stability relationship can be represented by a line with a slope of `45^(@),i.e.,` the maximum stability is attained when `n=Z` right of the curve. A radioactive nulide would be neutron rich and would decay by `beta-` emission to produce a daughter nucleus with a lower `n//p` ratio.
For heavier nuclides , `p-p` replusions start to offset the attractive forces and an excess of neutrons over proptons, required for stability.