What is the oxidation number of Mg in MgO?

• A. +1
• B. +2
• C. 0
• D. -2

Answer: (B)

Verified step by step guidance

1. Recall that the oxidation number of an element in its elemental form is 0, but in compounds, it depends on the element's typical charge and bonding behavior.
2. Identify the common oxidation states of oxygen, which is usually -2 in most compounds except in peroxides or when bonded to fluorine.
3. Since MgO is an ionic compound composed of Mg and O, and oxygen typically has an oxidation number of -2, assign oxygen an oxidation number of -2.
4. Use the fact that the compound MgO is electrically neutral, so the sum of the oxidation numbers must be zero.
5. Set up the equation for the sum of oxidation numbers: let the oxidation number of Mg be x, then x + (-2) = 0. Solve for x to find the oxidation number of Mg.