Question

The oxidation number of Pt in [Pt(C$_2$H$_4$)Cl$_3$]$^-$ is

• A. +1
• B. +2
• C. +3
• D. +4

Hint:

Always remember: neutral ligands like H$_2$O, NH$_3$, C$_2$H$_4$ contribute zero charge.

Answer 1

The Correct Option is B

Step 1: Assign charges to ligands.
- Ethylene (C$_2$H$_4$) is a neutral ligand.
- Chloride (Cl$^-$) has charge $-1$. There are 3 chlorides, so total = $-3$.
Step 2: Apply oxidation number rule.
Let the oxidation number of Pt be $x$. The overall charge is $-1$. \[ x + (0 \times 1) + (-1 \times 3) = -1 \] \[ x - 3 = -1 \quad \Rightarrow \quad x = +2 \] Step 3: Conclusion.
The oxidation number of Pt in [Pt(C$_2$H$_4$)Cl$_3$]$^-$ is +2.