Question

What is the oxidation state of chromium in ${\left[ {Cr{{\left( {{H_2}O} \right)}_6}} \right]^{3 + }}$?

Answer 1

Hint: The oxidation state of a metal atom in a coordination compound refers to the total amount of charge present on the central metal atom. We can find the oxidation state of a metal atom by equating the algebraic sum of the oxidation state of all atoms equal to the total positive or negative charge present on the coordinate ion.

Complete Step By Step Answer:
The oxidation state of a central metal atom refers to the total number of electrons lost or gained by it while forming a compound. We can also say that oxidation state is the measure of degree of oxidation of an atom within the compound. Let us assume oxidation state of chromium be x , then it can be founded as:
$ \Rightarrow {\text{ }}x{\text{ + }}0 \times 6{\text{ = + 3}}$ (Since the oxidation state of water molecule is considered to be zero)
$ \Rightarrow {\text{ }}x{\text{ = + 3}}$
Hence the oxidation state of chromium metal in the compound ${\left[ {Cr{{\left( {{H_2}O} \right)}_6}} \right]^{3 + }}$ is ${\text{ + 3}}$. Oxidation state of a metal atom is sometimes also known as the oxidation number. The oxidation state of metal atoms can be negative, zero and positive. Oxidation state of a metal atom cannot be a fractional number.

Note:
The oxidation state of a water molecule is considered to be zero since it is a neutral ligand. Neutral ligands do not have any charge on it. We can also find the oxidation state of chromium in the given compound by looking at the charge of ions. Since a water molecule has no charge therefore the oxidation of chromium will be equal to the total charge of the ion. But it is advised to use algebraic equation methods so as to avoid chances of errors.