The metal that shows highest and maximum number of oxidation state is :

Solution

Chemistry ma’am · 3 steps

Count the 4s and 3d electrons the metal can give away: Mn has seven, more than anyone else here.

1. Where states come from. In the 3d series, the 4s and 3d electrons are close in energy, so the metal can lose any number of them. The highest oxidation state usually equals the total of 4s and 3d electrons, up to manganese.
2. Why Mn peaks. Mn is 3d⁵ 4s², so all seven electrons are unpaired or easy to remove, giving +7 as in KMnO₄. After Mn the d electrons start pairing, and fewer of them can be used in bonding.

   Metal	Configuration	Oxidation states	Highest	How many
   Ti	3d² 4s²	+2, +3, +4	+4	3
   Mn	3d⁵ 4s²	+2, +3, +4, +5, +6, +7	+7	6
   Fe	3d⁶ 4s²	+2, +3, +4, +5, +6	+6	5
   Co	3d⁷ 4s²	+2, +3, +4	+4	3

3. So. Manganese wins on both counts: the highest state (+7) and the most states (six, from +2 to +7). The answer is (b).

The idea to keep. Across the 3d series, the number of oxidation states rises up to Mn (3d⁵ 4s²) and then falls, because paired d electrons are harder to use. Mn is the peak with +7.

Answer from the NTA final answer key. Solution by PrepWiser.