Question

Which of the following elements exhibits maximum number of oxidation states ?

• A. Scandium
• B. Zinc
• C. Manganese
• D. Cobalt

Hint:

Mn has five unpaired d electrons and shows every state from +2 to +7. Sc and Zn show only one state.

Answer 1

The Correct Option is C

Step 1: Link oxidation states to unpaired d electrons:
A 3d metal can use its 4s electrons and its unpaired 3d electrons for bonding.
The more unpaired electrons it has, the more oxidation states it shows. The count rises up to the middle of the series, around \( d^5 \).

Step 2: Check scandium.
Sc is \( 3d^1 4s^2 \). After losing three electrons it has an empty d shell, so it shows only +3.

Step 3: Check zinc.
Zn is \( 3d^{10} 4s^2 \). The d shell is full and stable, so only the two 4s electrons are lost. Zinc shows only +2.

Step 4: Check manganese.
Mn is \( 3d^5 4s^2 \) with five unpaired d electrons. It shows +2, +3, +4, +5, +6 and +7, which is six states.
For example \( \mathrm{MnCl_2} \) (+2), \( \mathrm{MnO_2} \) (+4), \( \mathrm{K_2MnO_4} \) (+6) and \( \mathrm{KMnO_4} \) (+7).

Step 5: Check cobalt.
Co is \( 3d^7 4s^2 \). It mainly shows +2 and +3, with +4 only in rare cases. That is far fewer than Mn.

Final Answer:
Manganese shows the widest range of oxidation states, from +2 to +7. \[ \boxed{\text{(C) Manganese}} \]