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
Statement I is incorrect but statement II is correct
Both the statements I and II are correct
Both the statements I and II are incorrect
Statement I is correct but statement II is incorrect
Show Solution
The Correct Option isA
Solution and Explanation
To determine the correct answer, let's analyze both statements individually using our knowledge of Chemistry, specifically periodic trends and electronic configuration.
Statement I: "The decrease in first ionization enthalpy from B to Al is much larger than that from Al to Ga."
The ionization enthalpy is the energy required to remove an electron from an atom in its gaseous state. It generally decreases down a group due to the increase in atomic size, which results in a decrease in the effective nuclear charge.
For group 13 elements, the atomic numbers of B (Boron), Al (Aluminum), and Ga (Gallium) are 5, 13, and 31, respectively. As we move from Boron to Aluminum, there is a significant drop in ionization energy. However, the drop in ionization energy is much smaller from Aluminum to Gallium.
The decrease in ionization enthalpy from B to Al is primarily due to an increase in atomic size and shielding effect provided by additional electron shells.
From Al to Ga, while there's also an increase in atomic size, the presence of filled d-orbitals in Gallium (which do not effectively shield the nuclear charge) counters the typical trend, resulting in a less pronounced decrease in ionization enthalpy.
This means the decrease from B to Al is not necessarily "much larger" than from Al to Ga, thus making Statement I incorrect.
Statement II: "The d orbitals in Ga are completely filled."
Gallium (Ga) has an electronic configuration: [Ar] \, 3d^{10} \, 4s^2 \, 4p^1. This shows that its d-orbitals are indeed completely filled with 10 electrons.
This is due to the transition metals preceding it in the periodic table, resulting in filled d-orbitals, confirming Statement II is correct.
Based on the above analysis:
Statement I is incorrect because the decrease in first ionization enthalpy from B to Al is not significantly larger than from Al to Ga.
Statement II is correct because the d-orbitals in Gallium are completely filled.
Therefore, the most appropriate answer is: "Statement I is incorrect but statement II is correct."
