Question

The incorrect statement Among the following is A)The first ionisation potential of Al is less than the first ionisation potential of Mg. B)The first ionisation potential of Na is less than the first ionisation potential of Mg. C)The second ionisation potential of Mg greater than the second ionisation potential of Na D)The third ionisation potential of Mg greater than the third ionisation potential of Al
A. The first ionization potential of Al is less than the first ionization potential of Mg
B. The second ionization potential of Mg is greater than the second ionization potential of Na
C. The first ionization potential of Na is less than the first ionization potential of Mg
D. The third ionization of Mg is greater than third ionization of Al

Answer 1

Correct Answer - B
Ionization potential or energy (IE) increases across a period but with certain breaks. `IE_(1)` of `Al(3s^(1)p^(1))` is less than `IE_(1)` of `Mg(3s^(2))` as electron is to be removed from 3p which is easy as compared to 3s. Further `IE_(3)` shows the reverse trend because now for `Al^(2+)(3s^(1))` electon is to be removed from 3s as compared to the completely filled 2p orbitals in `Mg^(2+)`. The same becomes true for `IE_(2)` of Na, hence option (b) is correct.