Classification of Elements and Periodicity Class 11 Chemistry Notes – Formulas & Quick Revision

Periodicity mein periodic table ke trends — atomic radius, ionisation enthalpy, electronegativity — cover hote hain. Ratta nahi, logic ka chapter. Yahan aapko is chapter ke sabse important formulas aur quick revision points free milte hain — NCERT/CBSE syllabus ke hisaab se, boards aur JEE/NEET dono ke liye.

Important Formulas & Concepts — Classification of Elements and Periodicity

• Atomic radius: period mein left→right ghatta hai, group mein upar→neeche badhta hai
• Ionisation enthalpy: period mein badhti hai, group mein ghatti hai
• Electron gain enthalpy: Cl ka sabse negative (F se bhi zyada)
• Electronegativity (Pauling): F = 4.0 maximum
• Effective nuclear charge Z_eff = Z − σ (Slater shielding)
• Isoelectronic species: zyada nuclear charge = chhota size
• Metallic character: group mein neeche badhta hai
• Oxide nature: left basic → right acidic (Al₂O₃ amphoteric)

Quick Revision Points

• N ki IE₁ O se zyada hai (half-filled 2p³ stability)
• Noble gases ka size van der Waals radius se — comparison mat karo
• 2nd period elements anomalous behaviour dikhate hain
• Diagonal relationship: Li-Mg, Be-Al, B-Si
• Trends ke exceptions hi exam questions bante hain

FAQ

Exceptions kaise yaad rakhun?

Complete PDF mein har trend ke exceptions colour-coded boxes mein highlighted hain.

NEET mein isse kya aata hai?

IE order, radius comparison aur oxide nature — har saal 1-2 questions.

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