⚡ Electronegativity – Complete Concept

📌 1️⃣ Definition

Electronegativity is the tendency of an atom in a molecule to attract the shared pair of electrons toward itself.

👉 It is not for isolated atoms, only for atoms in a bond.

📊 2️⃣ Important Scales

• Pauling Scale (most used in JEE)
  • Fluorine (F) = 4.0 (highest)
• Other scales:
  • Mulliken
  • Allred-Rochow

🔥 3️⃣ Key Characteristics

• No unit (dimensionless quantity)
• Depends on:
  • Atomic size
  • Nuclear charge
  • Hybridization
  • Oxidation state

📈 4️⃣ Periodic Trends

Across a Period (→)

• Increases
• Reason: Increase in nuclear charge

Down a Group (↓)

• Decreases
• Reason: Increase in atomic size

⚠️ 5️⃣ Important Exceptions / Special Cases

• Noble gases → usually no electronegativity (inert)
• Transition metals → irregular trend
• F is highest, but Cl sometimes shows stronger bonding behavior in some compounds

🧪 6️⃣ Factors Affecting Electronegativity

🔹 1. Atomic Size

• Smaller atom → higher electronegativity

🔹 2. Effective Nuclear Charge

• Higher charge → stronger attraction

🔹 3. Hybridization

sp>sp2>sp3sp > sp^2 > sp^3sp>sp2>sp3

👉 Example:

• C (sp) > C (sp²) > C (sp³)

🔹 4. Oxidation State

• Higher oxidation state → higher electronegativity

🧬 7️⃣ Applications in Compounds (Very Important)

🔹 1. Bond Type Prediction

Difference in electronegativity (ΔEN):

👉 Example:

• H₂ → non-polar
• HCl → polar
• NaCl → ionic

🔹 2. Bond Polarity

• Higher EN difference → higher polarity

👉 Example:

• O–H bond is polar
• C–H bond is almost non-polar

🔹 3. Dipole Moment

• Electronegativity determines direction of dipole

👉 Example:

• In HCl → Cl is δ⁻, H is δ⁺

🔹 4. Acidic and Basic Nature

• High electronegativity → acidic character increases

👉 Example:

• CH₄ < NH₃ < H₂O < HF (acidity increases)

🔹 5. Inductive Effect (Organic Chemistry)

• Electron-withdrawing groups (-I effect) depend on EN

👉 Example:

• -NO₂, -Cl → strong -I effect

🔹 6. Stability of Compounds

• Higher EN → stronger bond attraction

👉 Example:

• HF is more stable than HI

🔹 7. Reactivity of Elements

• High EN → strong oxidizing agents

👉 Example:

• F₂ is strongest oxidizing agent

🔹 8. Metallic vs Non-metallic Character

• Low EN → metallic nature
• High EN → non-metallic nature

🧠 8️⃣ Comparison with Electron Gain Enthalpy

🎯 9️⃣ JEE Important Points

• Fluorine = highest EN
• Trend questions are very common
• Hybridization effect → very important for advanced level
• Used in:
  • Bond polarity
  • Organic reactions
  • Acid-base strength

🧩 10️⃣ Quick Memory Tricks

👉 “F is the boss of electronegativity”
👉 Across ↑, Down ↓

🚀 Final Summary

• Electronegativity controls:
  • Bond type
  • Polarity
  • Reactivity
  • Acid-base nature
• It is one of the most important concepts in chemistry