Question

The oxidation number of underlined element in $\underset{–}{Ca}{\left(Cl{O}_2\right)}_2$ compound is :

• A. $+3$
• B. $+5$
• C. $-2$
• D. $+2$

Answer 1

The correct option is D $+2$

Let $x$ be the oxidation number of $Ca$ in $\underset{–}{Ca}{\left(Cl{O}_2\right)}_2$.

We know that the oxidation no. of oxygen = $-2$ but for Cl the oxidation no. is unknown. So, first, we need to find out the oxidation no. of Chlorine.

From the structure, we can see that Ca is attached with 2 $Cl{O}_2^{-}$ ions.

Let oxidation no. of Cl be $Q$,

So, $Q+2\times (-2)=-1$

$\Rightarrow Q=+3$

Since, the overall charge on the complex is $0$, the sum of oxidation states of all elements in it should be equal to $0$.

$x+2(+3+2(-2\left)\right)=0$
$x-2=0$
$x=+2$
Thus, the oxidation number of $Ca$ in $\underset{–}{Ca}{\left(Cl{O}_2\right)}_2$ is $+2$.

Hence, the correct option is D.