The correct order of the first ionization enthalpy is

We need to find the correct order of first ionization enthalpy for Group 13 elements.

The first ionization enthalpies (in kJ/mol, approximate) for Group 13 elements are:

B: 801, Al: 577, Ga: 579, In: 558, Tl: 589

The general trend down a group is decreasing IE due to increasing atomic size and shielding. However, anomalies exist:

Ga vs Al: Ga (579) has slightly higher IE than Al (577) due to poor shielding by the 3d electrons in Ga, leading to higher effective nuclear charge.

Tl vs Ga: Tl (589) has higher IE than Ga (579) due to the poor shielding effect of 4f electrons (lanthanide contraction) and relativistic effects on the 6s electrons.

Among the given options, the order $$Tl > Ga > Al$$ (589 > 579 > 577) is correct.

The correct answer is Option C: $$Tl > Ga > Al$$.