Given below are two statements:
Statement I: The decrease in first ionization enthalpy from B to Al is much larger than that from Al to Ga.
Statement II: The d orbitals in Ga are completely filled.
In the light of the above statements, choose the most appropriate answer from the options given below

We need to evaluate two statements about ionization enthalpy and electron configuration.

Statement I: The decrease in first ionization enthalpy from B to Al is much larger than that from Al to Ga.

The first ionization enthalpies (approximate values in kJ/mol) are:

B $$\approx 801$$, Al $$\approx 577$$, Ga $$\approx 579$$

Decrease from B to Al: $$801 - 577 = 224$$ kJ/mol

Decrease from Al to Ga: $$577 - 579 = -2$$ kJ/mol (actually a slight increase!)

The decrease from B to Al is indeed much larger than from Al to Ga. Statement I is TRUE.

The reason: From Al to Ga, the intervening $$3d$$ electrons provide poor shielding, so the effective nuclear charge increases, counteracting the effect of the additional shell.

Statement II: The d orbitals in Ga are completely filled.

Ga has the electron configuration: $$[\text{Ar}] \, 3d^{10} \, 4s^2 \, 4p^1$$

The $$3d$$ subshell has all 10 electrons, so it is completely filled. Statement II is TRUE.

Conclusion: Both Statement I and Statement II are correct.

The correct answer is Option B: Both the statements I and II are correct.