Variable Oxidation States
Transition elements commonly exhibit variable oxidation states, unlike most main-group metals; what feature of their electronic structure allows this?
Select the correct option:
Solution
Closeenergiesofnsand(n−1)delectronsallowingbothtoparticipate
The variable oxidation states of transition elements arise from the closeness in energy of the outer ns and the inner (n-1)d electrons. Because these two sets of electrons have comparable energies, both can be lost or involved in bonding, and the number of electrons participating can vary from one compound to another. This gives transition metals a range of oxidation states differing by one, such as iron showing +2 and +3 or manganese showing +2 up to +7. The option of equal energies of s and p orbitals is irrelevant, since the key is the ns and (n-1)d comparison. The option of absence of valence electrons is false, as transition metals have valence electrons. The option of fully filled d-orbitals would actually restrict variability. This basis for variable valency is a foundational NCERT property of the d-block. Plausibility check: manganese, with its 3d^5 4s^2 configuration, indeed shows the widest range of oxidation states up to +7, consistent with both ns and (n-1)d electrons being available.
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About This Question
- Subject
- chemistry
- Chapter
- d- and f-block elements
- Topic
- variable oxidation states
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
Closeenergiesofnsand(n−1)delectronsallowingbothtoparticipate
The variable oxidation states of transition elements arise from the closeness in energy of the outer ns and the inner (n-1)d electrons. Because these two sets of electrons have comparable energies, both can be lost or involved in bonding, and the number of electrons participating can vary from one compound to another. This gives transition metals a range of oxidation states differing by one, such as iron showing +2 and +3 or manganese showing +2 up to +7. The option of equal energies of s and p orbitals is irrelevant, since the key is the ns and (n-1)d comparison. The option of absence of valence electrons is false, as transition metals have valence electrons. The option of fully filled d-orbitals would actually restrict variability. This basis for variable valency is a foundational NCERT property of the d-block. Plausibility check: manganese, with its 3d^5 4s^2 configuration, indeed shows the widest range of oxidation states up to +7, consistent with both ns and (n-1)d electrons being available.
This easy difficulty chemistry question is from the chapter d- and f-block elements, covering the topic of variable oxidation states. It appeared in the 2025 exam.
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