Electron Affinity Explained | Class 11 Chemistry | JEE NEET Friendly

 

📚 What is Electron Affinity? (इलेक्ट्रॉन आफ़िनिटी क्या है?)

Electron Affinity ek atomic property hai jo batati hai ki kisi atom ko ek electron receive karne par kitni energy release hoti hai.

📌 Definition:

> Electron Affinity is the amount of energy released when an isolated neutral atom in the gaseous state accepts an extra electron to form a negative ion.

🔍 Example:

Chlorine (Cl) + e⁻ → Cl⁻ + Energy released

Yahan, energy release hoti hai = Electron Affinity

⚙️ Why Electron Affinity is Important?

Predict karta hai reactivity of non-metals

Help karta hai chemical bond samajhne me

Periodic trends ko samajhne ke liye crucial hai

📊 Trends in Electron Affinity in the Periodic Table:

🔼 Across a Period (Left to Right):

Electron Affinity increases

Reason: Nuclear charge badhta hai, atomic size kam hota hai

➡️ Atoms electrons ko strongly attract karte hain

> Example:

Na < Mg < Al < Si < P < S < Cl

Chlorine ki electron affinity sabse zyada hoti hai

🔽 Down a Group (Top to Bottom):

Electron Affinity decreases

Reason: Atomic size badhta hai, outer electrons nucleus se door hote hain

> Example:

F > Cl > Br > I > At

(Par exception bhi hota hai - dekho niche)

⚠️ Exceptions in Electron Affinity:

Fluorine ka size bahut chhota hota hai, isliye extra electron par repulsion hota hai

➡️ Is wajah se Chlorine ki Electron Affinity Fluorine se zyada hoti hai

🔍 Electron Affinity vs Electronegativity:

Property Electron Affinity Electronegativity

Kya measure karta hai? Energy released on gaining 1 electron Tendency to attract shared electrons

Type Measured value (kJ/mol) Relative scale (Pauling scale)

Affects Ion formation Bond polarity

🔬 Numerical Values (Approx.):

Element Electron Affinity (kJ/mol)

Fluorine (F) -328

Chlorine (Cl) -349 ✅

Oxygen (O) -141

Sulfur (S) -200

Nitrogen (N) ≈ 0 (due to stable half-filled orbital) ❌

📌 Important Points to Remember:

Electron Affinity is usually negative, as energy is released

Noble gases have zero or positive electron affinity (they don’t want extra electrons)

High EA = More tendency to form anions

🧠 Trick to Learn:

> “Cl loves electrons most, F looks small but gets stressed!”

(Chlorine has highest EA, Fluorine faces electron repulsion)

🎯 Best for JEE & NEET Revision:

Asked in Match the Column, Assertion-Reason, Conceptual MCQs

Remember the trend:

“Left → Right: Increase | Top → Bottom: Decrease”

🔚 Conclusion:

Electron Affinity ek key concept hai jo non-metal reactivity, ionic bonding, aur periodic behavior ko clearly explain karta hai. Chlorine is the king of Electron Affinity, and this concept can boost your Chemistry score in both JEE and NEET.