Question

What are the oxidation numbers of copper? Give examples.

Answer 1

Oxidation number:

• It is defined as the number of unpaired electrons present in the atom of an element that is available for bonding.
• Transition elements show variable oxidation states as they can use s electron as well as d electron.
• Copper $\left(\mathrm{Cu}\right)$ is a transition metal.

Oxidation number of Copper$\left(\mathrm{Cu}\right)$:

• The atomic number of Cu is 29.
• its electronic configuration be like $\left[\mathrm{Ar}\right]3{\mathrm{d}}^{9}4{\mathrm{s}}^2$ (less stable) and $\left[\mathrm{Ar}\right]3{\mathrm{d}}^{10}4{\mathrm{s}}^1$ (more stable)
• It can lose one electron from outer 4s or both electrons from 4s or both electrons from 4s plus one electron from 3d
• Hence $\mathrm{Cu}$ can exist in three oxidation numbers that are $1,+2\mathrm{and}+3$.
• The most common oxidation number of $\mathrm{Cu}$ is $+2$.

Steps for calculating oxidation number:

• Determine whether the ion/molecule is neutral or charged.
• Set the oxidation numbers in a compound equal to a compound's charge.
• Find atoms without oxidation number rules.
• Find the known oxidation number for the other elements in the compound.
• Multiply the number of each atom by its oxidation number.
• Add the results together.

Examples of Copper with different oxidation numbers:

• The oxidation number of Cu in Copper chloride $\left({\mathrm{CuCl}}_2\right)$ and Copper oxide $\left(\mathrm{CuO}\right)$ is $+2$.
• The oxidation number of Cu in Cuprous chloride $\left(\mathrm{CuCl}\right)$ is $+1$.
• The oxidation number of Cu in Potassium hexafluoro cuprate(III) $\left({\mathrm{K}}_3{\mathrm{CuF}}_6\right)$ is $+3$.