Anand Classes brings you a detailed explanation of the Periodic Variation of Electronegativity for Class 11, NEET, and JEE aspirants. Electronegativity is a fundamental concept in chemistry that helps us understand how atoms attract shared electrons in a covalent bond. In this study material, we explain how electronegativity changes across a period and down a group in the periodic table, along with its relation to atomic size, effective nuclear charge, and ionization enthalpy. This topic is extremely important for competitive exams as well as CBSE board preparation. Click the print button to download study material and notes.
Periodic Variation of Electronegativity
Electronegativity is the tendency of an atom to attract the shared pair of electrons towards itself in a covalent bond. Its value is not fixed for an atom but depends on its position in the Periodic Table.
Across a Period (Left → Right):
- As we move from left to right in a period, the atomic number increases.
- This leads to an increase in effective nuclear charge (more protons pulling the electrons).
- At the same time, the atomic size decreases (electrons are drawn closer to the nucleus).
- Due to stronger nuclear pull and smaller size, atoms attract shared electrons more strongly.
👉 Result: Electronegativity increases across a period.
Example: Li < Be < B < C < N < O < F
(b) Down a Group (Top → Bottom):
- As we move down a group, the number of electron shells increases.
- This causes the atomic size to increase, so the bonding electrons lie farther away from the nucleus.
- The effect of increasing nuclear charge is overshadowed by the shielding effect of inner electrons.
- Hence, the attraction of the nucleus for the bonding electrons becomes weaker.
👉 Result: Electronegativity decreases down a group.
Example: F > Cl > Br > I
Great! ✅ I see you want to present Table 19: Electronegativity values of some elements in a neat, well-structured, and student-friendly format. Let me rewrite it in a clear tabular form (SEO + study material friendly).
Table : Electronegativity Values of Some Elements (Pauling Scale)
Table below shows Electronegativity values of some important elements :
| Element | H | Li | Be | B | C | N | O | F |
|---|---|---|---|---|---|---|---|---|
| Value | 2.1 | 1.0 | 1.5 | 2.0 | 2.5 | 3.0 | 3.5 | 4.0 |
| Element | Na | Mg | Al | Si | P | S | Cl |
|---|---|---|---|---|---|---|---|
| Value | 0.9 | 1.2 | 1.5 | 1.8 | 2.1 | 2.5 | 3.0 |
| Element | K | Ca | Ga | Ge | As | Se | Br |
|---|---|---|---|---|---|---|---|
| Value | 0.8 | 1.0 | 1.6 | 1.8 | 2.0 | 2.4 | 2.8 |
| Element | Rb | Sr | In | Sn | Sb | Te | I |
|---|---|---|---|---|---|---|---|
| Value | 0.8 | 1.0 | 1.7 | 1.7 | 1.9 | 2.1 | 2.4 |
| Element | Cs | Ba | Tl | Pb | Bi | Po | At |
|---|---|---|---|---|---|---|---|
| Value | 0.7 | 0.9 | 1.8 | 1.7 | 2.0 | 1.9 | 2.2 |
FAQs on Periodic Variation of Electronegativity
Q1. What is electronegativity?
Electronegativity is the tendency of an atom to attract the shared pair of electrons towards itself in a covalent bond.
Q2. Why does electronegativity increase across a period?
Across a period, the effective nuclear charge increases and the atomic size decreases. This makes the nucleus pull the bonding electrons more strongly, so electronegativity increases.
Q3. Why does electronegativity decrease down a group?
Down a group, the atomic size increases and the shielding effect weakens the nucleus’ pull on bonding electrons. Hence, electronegativity decreases.
Q4. Which element has the highest electronegativity?
Fluorine (F) has the highest electronegativity value (3.98 on the Pauling scale).
Q5. Which elements have the lowest electronegativity?
Alkali metals such as Cesium (Cs) and Francium (Fr) show the lowest electronegativity values.
Q6. Is electronegativity the same as electron affinity?
No.
- Electronegativity: Tendency of an atom to attract shared electrons in a bond.
- Electron affinity: Energy released when a neutral atom accepts an extra electron.
Q7. How is the trend of electronegativity similar to ionization enthalpy?
Both increase across a period and decrease down a group, since both depend on atomic size and effective nuclear charge.
Q8. Why is Fluorine more electronegative than Oxygen?
Fluorine is smaller in size and has a higher effective nuclear charge than Oxygen, making it more electronegative.
Key Points / Conclusion:
- Across a period: Electronegativity increases (due to smaller size + higher nuclear charge).
- Down a group: Electronegativity decreases (due to larger size + shielding effect).
- Lowest Electronegativity: Alkali metals (Group 1)
- Highest Electronegativity: Halogens (Group 17), with Fluorine (F) being the most electronegative element.
✨ Do You Know?
- Fluorine has the highest electronegativity value (3.98 on Pauling scale).
- Cesium (Cs) and Francium (Fr) have among the lowest electronegativities.
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