In a compound formed from a metal and a non-metal, what are the typical oxidation numbers for metal and non-metal?

• A. Metal has positive oxidation number and the non-metal negative.
• B. Metal negative oxidation number; non-metal positive
• C. Both positive
• D. Both negative

Answer: (A)

In compounds formed from a metal and a non-metal, the metal tends to lose electrons while the non-metal tends to gain electrons. This creates ions: the metal becomes positively charged (positive oxidation number) and the non-metal becomes negatively charged (negative oxidation number). The whole compound must be electrically neutral, so the positive and negative charges balance. Examples like NaCl (Na⁺ with Cl⁻) and MgO (Mg²⁺ with O²⁻) show this pattern clearly. If both were positive or both negative, or if the metal were negative and the non-metal positive, the charges wouldn’t balance to zero, so those scenarios don’t fit the usual ionic compound behavior.