Read the following passage and answer the next five questions based on it.
| Sc | Ti | V | Cr | Mn | Fe | Co | Ni | Cu | Zn |
| Y | Zr | Nb | Mo | Tc | Ru | Rh | Pd | Ag | Cd |
| La | Hf | Ta | W | Re | Os | Ir | Pt | Au | Hg |
In any transition series, as we move from left to right the d-orbitals are progressively filled and their properties vary accordingly.
| Ce | Pr | Nd | Pm | Sm | Eu | Gd | Tb | Dy | Ho | Er | Tm | Yb | Lu |
| Th | Pa | U | Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No | Lr |
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 ?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Mn
In the first transition series the highest oxidation state an element can show is roughly the total number of its 4s and 3d electrons, up to the middle of the series. Beyond the middle the d electrons are held too firmly, and the number of oxidation states falls again.
Mn (Z = 25) is [Ar]3d54s2. It can use all seven electrons and shows every oxidation state from +2 to +7, as in \( \ce{KMnO4} \) and \( \ce{Mn2O7} \). This is the highest oxidation state in the first row.
Why the other options are incorrect
Option (1) Cr — Incorrect. Cr (Z = 24, [Ar]3d54s1) has six such electrons; its highest state is +6, as in \( \ce{K2Cr2O7} \).
Option (2) Fe — Incorrect. Iron commonly shows +2 and +3; its highest oxidation state is well below +7.
Option (4) V — Incorrect. V (Z = 23, [Ar]3d34s2) has five such electrons; its highest state is +5, as in \( \ce{V2O5} \).
NCERT (2026-27 edition):
Oxidation States – …
