Statement 1 The plot of atomic number ( $Y$-axis) versus number of neutrons ( $x$-axis) for stable nuclei shows a curvature towards $X$-axis from the line of $45^{\circ}$ slope as the atomic number is increased. Statement 2 Proton-proton electrostatic repulsions begin to overcome attractive forces involving protons and neutrons in heavier nuclides.

• Correct answer
  A

  Statement 1 is true, Statement 2 is true, Statement 2 is a correct explanation for Statement 1.
• B

  Statement 1 is true, Statement 2 is true, Statement 2 is not a correct explanation for Statement 1.
• C

  Statement 1 is true, Statement 2 is false.
• D

  Statement 1 is false, Statement 2 is true

Solution

The stability relationship can be represented by a line with a slope of $45^{\circ}$, i.e. the maximum stability is attained, when $N=Z$. Right or the curve a radioactive nuclide would be neutron rich and would decay be $\beta$-emission to produce a daughter nucleus with a lower $\frac{n}{p}$ ratio. For heavier nuclides, $p-p$ repulsions start to offset the attractive forces and an excess of neutrons over protons, is required for stability

Hence, the correct answer is option: 'A'.