Question

Actinoids show larger number of oxidation states :

• A. because they are radioactive in nature
• B. because they have large atomic numbers
• C. because they have large atomic masses
• D. due to comparable energies of 5f, 6d and 7s orbitals

Hint:

Actinoids show many oxidation states because the energies of 5f, 6d and 7s orbitals are very close, allowing electrons from all these orbitals to participate in bonding.

Answer 1

The Correct Option is D

Concept: Actinoids belong to the 5f-block of the periodic table. They exhibit a wide range of oxidation states because the energies of the 5f, 6d and 7s orbitals are very close to each other. As a result, electrons from all these orbitals can participate in bonding, leading to several possible oxidation states.

Step 1: Understanding oxidation states in actinoids. The electronic configurations of actinoids involve \[ 5f,\;6d,\;7s \] orbitals. Since these orbitals have nearly equal energies, electrons can be removed from different orbitals during bond formation.

Step 2: Reason for variable oxidation states. Because electrons from 5f, 6d and 7s orbitals can participate in bonding, actinoids exhibit oxidation states such as \[ +3,\;+4,\;+5,\;+6,\;+7 \] and others. This results in a larger number of oxidation states compared to lanthanoids.

Step 3: Evaluating the options. Radioactivity does not cause variable oxidation states. Large atomic number does not directly explain oxidation states. Large atomic mass is unrelated. The correct reason is the comparable energies of 5f, 6d and 7s orbitals. Therefore Option (D) is correct. \[ \boxed{\text{Option (D)}} \]