8.2 Organic chemistry isomerism — Chemistry STD 11 Science — Question

$M(s) \to M(g)\,\,\,\,\,\,\,\,\,\,\,\,\,\, ........(1)$

$M(s) \to M^{2+} (g) + 2e^-\,\,\,\,\,\,\,\,.......(2)$

$M(g) \to M^+(g) + e^-\,\,\,\,\,\,\,\,\,\,\,.........(3)$

$M^+ (g) \to M^{2+} (g) + e^-\,\,\,\,\,\,\,\,\,.........(4)$

$M(g) \to M^{2+} (g) +2e^-\,\,\,\,\,\,\,\,\,\,\,..........(5)$

The second ionization energy of $M$ could be calculated from the energy  values assoclated with