Read the following passage and answer the next five questions based on it:

In any transition series, as we move from left to right the \(d-\)orbitals are progressively filled and their properties vary accordingly

The above are the two series of f-block elements in which the chemical properties won't change much. The 5f-series elements are radioactive in nature and mostly are artificially synthesized in laboratories and thus much is not known about their chemical properties.

Why do the actinoids exhibit higher number of oxidation states than lanthanoids?

Energy difference between 5f and 6d is less with respect to the energy difference between 4f and 5d.

The correct answer is option 2. Energy difference between 5f and 6d is less with respect to the energy difference between 4f and 5d.

The correct explanation for why the actinoids exhibit a higher number of oxidation states than lanthanoids is option 2. Energy difference between 5f and 6d is less with respect to the energy difference between 4f and 5d.

In both actinoids and lanthanoids, the 4f and 5d orbitals are inner shell orbitals, while the 5f and 6d orbitals are outer shell orbitals. In actinoids, the energy difference between the 5f and 6d orbitals is relatively small compared to the lanthanoids, where the energy difference between the 4f and 5d orbitals is larger. This smaller energy difference in actinoids allows for greater overlap and mixing of the 5f and 6d orbitals, leading to a broader range of energetically accessible electronic configurations and oxidation states. As a result, actinoids can exhibit a wider variety of oxidation states compared to lanthanoids.

The smaller energy difference between the 5f and 6d orbitals in actinoids means that electrons can easily transfer between these orbitals to form different oxidation states. In contrast, the larger energy difference between the 4f and 5d orbitals in lanthanoids limits the extent of electron transfer between these orbitals, resulting in a narrower range of accessible oxidation states.

The ability of actinoids to adopt a wider range of oxidation states contributes to their greater chemical reactivity compared to lanthanoids.  Actinoids can participate in a broader array of chemical reactions due to their ability to readily change oxidation states, making them more versatile in various chemical environments.

In summary, the smaller energy difference between the 5f and 6d orbitals in actinoids, compared to the larger energy difference between the 4f and 5d orbitals in lanthanoids, allows actinoids to exhibit a greater variety of oxidation states, contributing to their higher reactivity and broader range of chemical behaviors.