Question

Write down the chemical formula of Copper nitrate.

Answer 1

The formula of copper nitrate depends on the oxidation number of the main element of the compound. In this question, the oxidation number of neither of the elements is given, so the oxidation number will be taken accordingly.

Complete Step By Step Answer:
The chemical formula of copper nitrate is $Cu{{(N{{O}_{3}})}_{2}}$ . Copper nitrate is also commonly known as cupric nitrate or copper dinitrate.
As the oxidation number of any element is not specified in the question, the oxidation number is taken in general. Thus, the oxidation number of nitrate ( $N{{O}_{3}}$ ) is -1, and there are two nitrate molecules in copper nitrate. Thus, the total oxidation number of nitrate molecules will be -2.
Generally, copper has an oxidation number of one as it has only one electron in its outermost orbit. But, in this compound nitrate has a total oxidation number of -2, thus the copper atom donates two electrons to two nitrate molecules respectively. So, the oxidation number of copper is +2.
Thus, another way to write the IUPAC name of $Cu{{(N{{O}_{3}})}_{2}}$ is Copper (II) nitrate. This shows that the oxidation number of copper is two.

Note:
The oxidation number of nitrogen in a nitrate molecule is +5, because the oxidation number of an oxygen atom is -2, so the oxidation number of 3 oxygen atoms will be -6. As nitrogen has 5 electrons in its outermost orbit, it can donate those 5 electrons to become stable.
Thus, total charge on one nitrate molecule will be-1. Also, as copper nitrate is an ionic compound, the overall charge will be zero.