The unexpected E⁰ values for Mn, Ni, and Zn are linked to their electronic configurations. The stability of half-filled d subshell (d⁵) in Mn²⁺ and completely filled d subshell (d¹⁰) in Zn is related to their E⁰ values, while for ...
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The decreasing tendency in E⁰ values for M²⁺/M reflects a trend towards less negative values across the transition metal series, which is associated with the increase in the sum of the first and second ionization enthalpies.
Noble transition metals are unaffected by single acids due to their low reactivity. In contrast, most first-series metals, excluding copper, are more reactive and undergo oxidation by 1M H⁺, albeit sometimes at a slow rate.
Oxygen’s ability to stabilize high oxidation states surpasses that of fluorine, as seen in the highest fluoride (MnF₄) and oxide (Mn₂O₇) of manganese, highlighting oxygen’s superiority in forming multiple bonds to metals.
The highest known oxide for iron is Fe₂O₃, and no higher oxides are known beyond Group 7. Although ferrates (VI) are formed in alkaline media, they readily decompose to Fe₂O₃ and O₂.
Oxygen’s ability to stabilize the highest oxidation state is evident in oxides, with the highest oxidation number coinciding with the group number, observed in Sc₂O₃ to Mn₂O₇.
The low third ionization enthalpy in Zn is due to the removal of one 4s electron, resulting in a stable d¹⁰ configuration. Removing electrons from d⁵ (Mn²⁺) and d¹⁰ (Zn²⁺) ions is challenging, leading to high third ionization enthalpies.
The high third ionization enthalpies of copper, nickel, and zinc indicate the difficulty in removing additional electrons, limiting their oxidation states to values not greater than two.
The low value for Sc reflects the stability of Sc³⁺, which possesses a noble gas configuration, highlighting the preference for achieving noble gas stability in its oxidation states.
The highest value for Zn is attributed to the removal of an electron from the stable d¹⁰ configuration of Zn²⁺, emphasizing the significance of achieving a fully filled d orbital for stability.