Which of the following elements is most likely to have an oxidation number of +2 in its compounds?

• A. Cl
• B. Mg
• C. Na
• D. Al

Answer: (B)

Verified step by step guidance

1. Understand that the oxidation number of an element in a compound reflects the charge it would have if all bonds were ionic. Elements tend to have common oxidation states based on their position in the periodic table and their electron configurations.
2. Look at the elements given: Cl (chlorine), Mg (magnesium), Na (sodium), and Al (aluminum). Identify their group numbers in the periodic table: Cl is in group 17, Mg in group 2, Na in group 1, and Al in group 13.
3. Recall that elements in group 2 (alkaline earth metals) typically lose two electrons to achieve a stable electron configuration, resulting in a +2 oxidation state. This is characteristic of magnesium (Mg).
4. Compare this with the other elements: Na (group 1) usually has a +1 oxidation state, Al (group 13) commonly has a +3 oxidation state, and Cl (group 17) usually has negative oxidation states like -1, though it can have positive states in some compounds but +2 is uncommon.
5. Conclude that Mg is the element most likely to have an oxidation number of +2 in its compounds because it naturally loses two electrons to form stable ionic compounds.