The bond formed between two elements with electron configurations 1s2 2s2 2p6 3s2 and 1s2 2s2 2p4 is

Step 1: Identify the elements

• 1s² 2s² 2p⁶ 3s²: 12 electrons, so this is magnesium (Mg), a Group 2 metal.
• 1s² 2s² 2p⁴: 8 electrons, so this is oxygen (O), a Group 16 non-metal.

Step 2: Think about the electron transfer

• Mg has 2 valence electrons (3s²). It loses them easily to reach the stable neon configuration, forming Mg²⁺.
• O has 6 valence electrons (2s² 2p⁴). It needs 2 more to complete its octet, forming O²⁻.

Step 3: Decide the bond type Mg is a metal with low electronegativity and O is a non-metal with high electronegativity. The large electronegativity difference means electrons are transferred from Mg to O, not shared. The oppositely charged ions Mg²⁺ and O²⁻ are held together by electrostatic attraction.

Mg + O → Mg²⁺ + O²⁻ → MgO (magnesium oxide)

This is an ionic (electrovalent) bond.

Why not the others?

• Metallic: occurs between atoms of metals only.
• Covalent: involves sharing of electrons, typically between two non-metals.
• Dative: a covalent bond where one atom supplies both electrons, as in NH₄⁺, which does not apply here.

Answer: D (ionic).

Exam tip: Metal + non-metal gives an ionic bond. Non-metal + non-metal gives a covalent bond. Always work out the element from the total number of electrons first. Here, 12 is Mg and 8 is O.