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

Step 1: Analyze the question We are given two elements by atomic number and asked what bond they form together.

Step 2: Find the electronic configurations

• X (atomic number 11): 2, 8, 1. This is sodium (Na), a metal with 1 valence electron.
• Y (atomic number 17): 2, 8, 7. This is chlorine (Cl), a non-metal with 7 valence electrons.

Step 3: Apply the concept

• A metal and a non-metal usually combine by electron transfer, which gives an ionic (electrovalent) bond.
• Non-metals bonding with non-metals share electrons, which gives a covalent bond.
• A dative bond needs one atom to supply both electrons of the shared pair (as in NH₄⁺).
• A metallic bond occurs between metal atoms only.

Step 4: Solution

• Na loses its 1 valence electron: Na → Na⁺ + e⁻ (now 2, 8, like neon).
• Cl gains that electron: Cl + e⁻ → Cl⁻ (now 2, 8, 8, like argon).
• The oppositely charged ions, Na⁺ and Cl⁻, attract each other strongly. This forms sodium chloride, NaCl, held together by an ionic bond.

Answer: C. Ionic

Tip: For bond-type questions, first identify the elements from their atomic numbers. A metal (Groups 1, 2, 3) plus a non-metal (Groups 6, 7) gives ionic. Two non-metals give covalent. Remember "Metal + Non-metal = Ionic".