Elements: Li, Be, B, C, N, O, F

These show properties different from the rest of their groups.

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Main Reasons

1. Very small atomic size
2. High ionization enthalpy
3. High electronegativity
4. No d-orbitals available (cannot expand octet)
5. High charge density / polarising power

Important Examples (Exam Focus)

Li (vs other Group 1)

• Forms Li₃N (others don’t easily)
• LiCl shows covalent character
• Li₂CO₃ decomposes on heating

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Be (vs other Group 2)

• Compounds are covalent
• BeO, Be(OH)₂ are amphoteric
• Strong complex formation

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B (vs other Group 13)

• Always covalent
• Does not form B³⁺ ion easily
• Forms electron-deficient compounds (e.g., BF₃)

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🔹 C, N, O, F

• Show strong pπ–pπ bonding
• Form multiple bonds (C=C, C≡C, N≡N, etc.)
• Higher electronegativity than heavier elements