If the elements X and Y have atomic numbers 11 and 17 respectively, what type of bond can they form?

Correct answer: Ionic.

Explanation: X has atomic number 11 (sodium, Na) and Y has atomic number 17 (chlorine, Cl). A metal (Na) tends to lose one electron to form Na⁺, while a non-metal (Cl) tends to gain one electron to form Cl⁻. The electrostatic attraction between Na⁺ and Cl⁻ forms an ionic bond.

• Dative (coordinate) – Incorrect. Requires one atom donating a lone pair to an empty orbital; not the usual bonding between Na and Cl.
• Covalent – Incorrect. Covalent bonding involves sharing electrons, common between non-metals with similar electronegativities; Na (metal) and Cl (non-metal) instead transfer an electron.
• Metallic – Incorrect. Occurs between metals only (delocalized “sea” of electrons), not between a metal and a non-metal.