Question

The most common oxidation states of chromium are

• A. \(+2,+7 \)
• B. \(+3,+6 \)
• C. \(+2,+4 \)
• D. \(+2,+5 \)
• E. \(+3,+5 \)

Hint:

+3 (stable), +6 (oxidizing) are most common for chromium.

Answer 1

The Correct Option is B

Step 1: Understanding Oxidation States of Transition Metals:
Transition metals, like chromium (Cr), exhibit variable oxidation states due to the participation of both ns and (n-1)d electrons in bonding. Chromium has an atomic number of 24, and its electron configuration is \([Ar] 3d^5 4s^1\). This half-filled d-orbital configuration provides extra stability.
Step 2: Analyzing Chromium's Oxidation States:
Chromium can lose electrons from both the 4s and 3d orbitals to form ions with various oxidation states.
+2 state: Formed by losing the 4s\(^1\) and one 3d electron (e.g., in CrCl\(_2\)). It is a reducing agent.
+3 state: Formed by losing the 4s\(^1\) and two 3d electrons, resulting in a stable \(t_{2g}^3\) configuration in an octahedral field. This is the most stable and one of the most common oxidation states of chromium (e.g., in Cr\(_2\)O\(_3\), CrCl\(_3\)).
+6 state: Formed by losing all six valence electrons (one 4s and five 3d). This is the highest oxidation state for chromium and is found in powerful oxidizing agents like chromate (CrO\(_4^{2-}\)) and dichromate (Cr\(_2\)O\(_7^{2-}\)). This is also a very common and important oxidation state.
While other states like +1, +4, and +5 exist, they are much less common and stable than +3 and +6.
Step 3: Final Answer:
The most common and chemically significant oxidation states of chromium are +3 (most stable) and +6 (important in oxidizing agents).