What is the charge of Hg in HgO?
The correct answer and explanation is:
The charge of mercury (Hg) in mercury(II) oxide (HgO) is +2.
Mercury can exist in two oxidation states: +1 and +2. In the compound mercury(II) oxide, the Roman numeral II in the name indicates that mercury is in the +2 oxidation state. The oxide ion (O) has a charge of -2, as oxygen typically forms anions with a -2 charge. In order for the compound to be electrically neutral, the positive charge on mercury must balance out the negative charge on oxygen. Therefore, the charge on mercury in this compound is +2.
To summarize:
- Oxidation states: Mercury in mercury(II) oxide has an oxidation state of +2, which corresponds to its +2 charge.
- Charge balance: The oxide ion has a charge of -2. For the compound to be neutral, the charges of mercury and oxygen must cancel out. A +2 charge on mercury balances the -2 charge on oxygen, resulting in an overall neutral compound.
- Naming convention: The name “mercury(II) oxide” is used to indicate that mercury is in the +2 oxidation state. This follows the naming system where the Roman numeral specifies the charge of the metal.
Mercury can also form compounds where it has a +1 charge, such as in mercury(I) chloride (Hg₂Cl₂), where two mercury ions each have a +1 charge. However, in HgO, the charge on mercury is +2, which is why it is referred to as mercury(II) oxide.