Question

Write the highest oxidation state of Cr and Mn.

• A. +2,+3
• B. +6,+7
• C. +4,-4
• D. +3,-5

Hint:

Maximum oxidation state in the first transition series generally corresponds to the group number. Chromium shows +6 and manganese shows +7.

Answer 1

The Correct Option is B

Concept: Transition elements exhibit variable oxidation states because both the \(ns\) and \((n-1)d\) electrons can participate in bonding. Chromium and manganese belong to the first transition series and possess several oxidation states. The highest oxidation state generally corresponds to the total number of valence electrons available for bonding.

Step 1: Determine the highest oxidation state of chromium. Electronic configuration of chromium: \[ Cr=[Ar]\,3d^5\,4s^1 \] Total valence electrons: \[ 5+1=6 \] Therefore chromium can exhibit a maximum oxidation state of: \[ \boxed{+6} \] Example: \[ CrO_4^{2-},\quad Cr_2O_7^{2-} \]

Step 2: Determine the highest oxidation state of manganese. Electronic configuration of manganese: \[ Mn=[Ar]\,3d^5\,4s^2 \] Total valence electrons: \[ 5+2=7 \] Thus manganese exhibits a maximum oxidation state of: \[ \boxed{+7} \] Example: \[ MnO_4^{-} \]

Step 3: Select the correct option. \[ Cr=+6 \] \[ Mn=+7 \] Hence, \[ \boxed{(2)} \] is the correct answer.