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Ashika
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Asked: 2024-08-02T12:28:04+05:30 In:

Why do transition elements show variable oxidation states? How is the variability in oxidation states of d-block different from that of the p-block elements?

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Why do transition elements show variable oxidation states? How is the variability in oxidation states of d-block different from that of the p-block elements?
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2 Answers

  1. Ashika
    Knowledge Contributor

    The energies of (n-1)d orbitals and ns orbitals are nearly identical in transition elements. As a result, electrons from both can participate in bond formation, resulting in variable oxidation states.

    In transition elements, the oxidation states differ from each other by unity. For e.g., Fe+2 and Fe+3, Cu+ and Cu2+, etc., whereas in p-block elements, the oxidation states differ by units of two, e.g., Sn2+ and Sn3+, Pb2+ and Pb4+, etc.

    Higher oxidation states in transition elements are more stable for heavier elements in a group. For e.g., Mo (VI) and W (VI) are more stable than Cr (VI) in group 6, whereas lower oxidation states in p-block elements are more stable for heavier elements due to the inert pair effect, e.g., Pb(Il) is more stable than Pb(IV) in group 16

  2. manali
    Knowledge Contributor

    Transition elements, which are also known as d-block elements, show variable oxidation states due to the involvement of their (n-1)d and ns electrons in bonding. This characteristic is a key feature of transition metals and is due to several factors:

    Reasons for Variable Oxidation States in Transition Elements
    Close Energy Levels of (n-1)d and ns Orbitals: The energy difference between the (n-1)d and ns orbitals is relatively small. As a result, both sets of electrons can be used for bonding, leading to various possible oxidation states.

    Stability of Half-Filled and Fully Filled Configurations: Transition metals tend to achieve more stable electron configurations, such as half-filled (d^5) or fully filled (d^10) subshells. The desire to attain these configurations can result in multiple oxidation states.

    Variable Bonding Situations: Transition metals can form a variety of complexes with different ligands. The ability to engage in complex formation can stabilize different oxidation states depending on the nature of the ligand field.

    Comparison with p-Block Elements
    p-Block Oxidation States: In p-block elements, the variability in oxidation states generally arises from the inert pair effect (for heavier elements) or the participation of ns and np electrons in bonding. The oxidation states of p-block elements are often more predictable and follow a regular pattern within a group (such as group 14 elements showing +2 and +4 oxidation states).

    Fewer Oxidation States: Unlike transition elements, p-block elements do not have d-orbitals that can participate in bonding within the same principal energy level, limiting the number of possible oxidation states. Their oxidation states usually range from -3 to +5, depending on the group and period.

    Inert Pair Effect: In heavier p-block elements, the ns^2 electrons are often less involved in bonding due to the inert pair effect, which reduces the number of accessible oxidation states, especially lower ones.

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