Which of the following best represents the Lewis dot structure for the ionic compound magnesium oxide (MgO)?

• A. Mg with two dots and O with six dots
• B. Mg^{+} with one dot and O^{-} with seven dots
• C. Mg^{2+} with no dots and O^{2-} with eight dots (a full octet)
• D. Mg with no dots and O with eight dots

Answer: (C)

Verified step by step guidance

1. Step 1: Understand that magnesium oxide (MgO) is an ionic compound formed between magnesium (Mg) and oxygen (O). Magnesium tends to lose electrons to achieve a stable electron configuration, while oxygen tends to gain electrons.
2. Step 2: Recall that magnesium is in Group 2 of the periodic table, so it has 2 valence electrons. It will lose these 2 electrons to form a Mg^{2+} ion, resulting in no dots around Mg in the Lewis structure.
3. Step 3: Oxygen is in Group 16 and has 6 valence electrons. It will gain 2 electrons (to complete its octet) to form an O^{2-} ion, which means it will have 8 dots (representing 8 valence electrons) around it in the Lewis structure.
4. Step 4: The Lewis structure for MgO should show Mg^{2+} with no dots (since it lost its valence electrons) and O^{2-} with eight dots (a full octet), indicating the transfer of electrons and the formation of ions.
5. Step 5: Confirm that this representation matches the ionic nature of MgO, where Mg^{2+} and O^{2-} ions are held together by electrostatic attraction, which is characteristic of ionic compounds.