Question

What would be the name of $Ni{{O}_{2}}$ ? What are the charges on each nickel cation? How does that translate into a name?

Answer 1

We know that at first think about the chemical formula of nickel oxide. The chemical formula of nickel oxide is $Ni{{O}_{2}}$. In the chemical formula of nickel oxide nickel exists in $+2$ oxidation state and oxygen exists in $-2$ oxidation state.

Complete answer:
Nickel oxide is the principal oxide of nickel. It is classified as basic metal oxide. It is a green crystalline solid. Nickel oxide adopts the sodium chloride structure with octahedral $N{{i}^{+2}}$ and ${{O}^{-2}}$ sites. Nickel oxide is also a component in the nickel-iron battery, also known as the Edison battery. It is a component in fuel cells. It is the precursor to many nickel salts.
To find the formula of the oxide, first write down the configuration of neutral nickel atoms. After that, find out the charge on the nickel ions for ${{d}^{8}}$ and ${{d}^{7}}$ configuration. Apply the concept of electro-neutrality.
Since $Ni{{O}_{2}}$ is an ionic compound, the first part of the name will be the name of the cation, Nickel. Since nickel is a transition metal, we must provide the oxidation state. Oxygen in ionic compounds usually exists in the -2 state, so nickel's charge will be $\dfrac{+2}{2atoms}=+1.$ This is added in the middle part of the name. Finally, the last part of the name comes from the name of anionic oxygen, oxide.
Therefore, Name of the compound will be Nickel $(I)$ Oxide and the charge it provides is $+1$ thus, it provides the $(I)$ to the name.
Heating nickel oxide with hydrogen, carbon or carbon monoxide reduces it to metallic nickel. It combines with the oxides of sodium and potassium at high temperatures to form the corresponding nickelate.

Note:
Remember that the chemical formula of nickel oxide is $Ni{{O}_{2}}$ because the fraction of nickel ions in $+2$ oxidation state dominates the fraction of $N{{i}^{+3}}$ ions. So the nickel exists in $+2$ oxidation state in its chemical formula.