Question

What is the oxidation number of gold in the complex $[AuC{l}_4{]}^{-}$ ?

• A. 4
• B. 3
• C. 2
• D. 1

Answer 1

The correct option is B 3

Let the oxidation state of $Au$ be $x$, $Cl$ has an oxidation state of $-1$ and the complex ion has a $-1$ charge as well:
$x+4(-1)=-1$
$x=+3$
Oxidation state of Au in $[AuC{l}_4{]}^{-}$ is $+3$