Question

Choose the transition element which exhibit least number of variable oxidation states.

• A. \(\mathrm{Sc}\)
• B. \(\mathrm{Cr}\)
• C. \(\mathrm{Mn}\)
• D. \(\mathrm{Fe}\)

Hint:

Scandium predominantly shows only \(+3\) oxidation state, whereas manganese exhibits the maximum number of oxidation states in the first transition series.

Answer 1

The Correct Option is A

Concept: Variable oxidation states arise due to the small energy difference between \((n-1)d\) and \(ns\) orbitals in transition elements. The greater the number of available electrons, the larger the number of oxidation states possible.

Step 1: Consider scandium.
Electronic configuration: \[ Sc=[Ar]\,3d^1 4s^2 \] The most stable oxidation state is \[ +3 \] Scandium rarely exhibits other oxidation states. Therefore it has the least variability.

Step 2: Consider chromium.
Chromium exhibits \[ +2,\ +3,\ +6 \] and several intermediate oxidation states.

Step 3: Consider manganese.
Manganese shows the largest range of oxidation states. \[ +2 \text{ to } +7 \]

Step 4: Consider iron.
Iron commonly exhibits \[ +2,\ +3 \] and a few additional oxidation states.

Step 5: Select the element showing minimum variability.
Among all the given elements, scandium exhibits the least number of oxidation states. \[ \boxed{\mathrm{Sc}} \]