Read the following passage and answer the next five questions based on it. (37-41)
Transition Series Elements:

Sc Ti V Cr MnFeCoNiCuZn

YZrNbMoTcRuRhPdAgCd
La Hf Ta WReOsIrPtAuHg

In any transition series, as we move from left to right the d-orbitals are progressively filled and their properties vary accordingly.
f-block Elements:

Ce Pr Nd PmSmEuGdTbDyHoErTmYbLu
Th Pa UNpPuAmCmBkCfEsFmMdNoLr

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.

Which metal has the highest oxidation state in the first row transition series?

The correct option is Mn.

To understand why manganese (Mn) has the highest oxidation state in the first-row transition series, let us look at the outer electronic configurations of the elements in this row:

The first-row transition metals (3d series) and their valence shell electronic configurations are:

Scandium (Sc): 3d¹ 4s²
Titanium (Ti): 3d² 4s²
Vanadium (V): 3d³ 4s²
Chromium (Cr): 3d⁵ 4s¹
Manganese (Mn): 3d⁵ 4s²
Iron (Fe): 3d⁶ 4s²
Cobalt (Co): 3d⁷ 4s²
Nickel (Ni): 3d⁸ 4s²
Copper (Cu): 3d¹⁰ 4s¹
Zinc (Zn): 3d¹⁰ 4s²

Transition metals exhibit variable oxidation states by losing or sharing electrons from both their outermost 4s subshell and the inner, partially filled 3d subshell, because these orbitals are very close in energy.

The maximum oxidation state of a transition metal in the first half of the series is typically determined by the sum of its 3d (unpaired) and 4s electrons. Manganese (Mn) has 5 unpaired electrons in the 3d subshell and 2 electrons in the 4s subshell, giving a total of 7 valence electrons.

As a result, manganese can show a range of oxidation states from +2 to +7. The +7 oxidation state is the highest oxidation state shown by any member of the 3d transition series (as seen in compounds like KMnO₄).

Beyond manganese, the pairing of d-orbitals begins, which reduces the number of unpaired d-electrons available for bonding. Consequently, the maximum oxidation state decreases in the subsequent elements (for example, Fe shows a maximum oxidation state of +6 under highly oxidizing conditions, but +2 and +3 are its most stable states).