Two elements X and Y with electronic configurations 2,8,2 and 2,8,7 respectively, are likely to combine by _________bonding

Step 1: Analyze the question We need to identify the type of bond formed between element X (2,8,2) and element Y (2,8,7).

Step 2: Identify the elements

• X: 2,8,2 has 12 electrons, so it is Magnesium (Mg), a metal in Group 2. It has 2 valence electrons.
• Y: 2,8,7 has 17 electrons, so it is Chlorine (Cl), a non-metal in Group 17. It has 7 valence electrons.

Step 3: Recall the concept

• A metal and a non-metal combine by electron transfer, which gives electrovalent (ionic) bonding.
• Two non-metals share electrons, which gives covalent bonding.
• Metal atoms with metal atoms give metallic bonding.

Step 4: Work through the bonding

• Mg loses its 2 outer electrons to achieve the stable octet: Mg → Mg²⁺ + 2e⁻ (configuration 2,8).
• Each Cl atom gains 1 electron: Cl + e⁻ → Cl⁻ (configuration 2,8,8).
• Two Cl atoms are needed to accept the 2 electrons from one Mg atom.
• The oppositely charged ions attract each other strongly, forming MgCl₂.

Step 5: Conclusion The bond formed is electrovalent (ionic), which is option C.

Why the others are wrong:

• A (covalent): needs two non-metals sharing electrons.
• B (dative): one atom supplies both electrons of the shared pair, which doesn't apply here.
• D (hydrogen): a weak intermolecular attraction involving H bonded to N, O, or F.
• E (metallic): occurs only between metal atoms.

Exam tip: Quickly count the outer electrons. If one element has 1-3 outer electrons (metal) and the other has 5-7 (non-metal), expect electrovalent bonding. Remember: Metal + Non-metal = Ionic.