Why does electronegativity decrease down the group?

1. Why does electronegativity decrease down the group? +

Correct Answer

Electronegativity decreases down a group mainly because atomic size and shielding effect increase.

Detailed Explanation

Electronegativity is the tendency of an atom to attract the shared pair of electrons towards itself in a chemical bond. When we move from top to bottom in a group, new electron shells are added. As a result, the valence shell becomes farther from the nucleus and the attraction between the nucleus and bonding electrons decreases.

Down the group → Number of shells ↑ → Atomic radius ↑

Therefore, the nucleus has less effective attraction for the shared electron pair.

Atomic size ↑ → Attraction for bonding electrons ↓ → Electronegativity ↓

Main Reasons

1. Increase in Atomic Radius
Each step downward adds an electron shell. The valence electrons therefore move farther away from the nucleus.

2. Increase in Shielding Effect
The inner electrons increasingly shield the valence electrons from the attraction of the nucleus.

3. Decrease in Effective Nuclear Attraction
Although nuclear charge increases down the group, the additional shells and shielding largely reduce the attraction experienced by the bonding electrons.

Shielding ↑ + Distance from nucleus ↑ → Electronegativity ↓

Example: Halogens

For Group 17:

F > Cl > Br > I

Fluorine is the most electronegative because it has the smallest atomic size among these elements. As we move downward:

F → Cl → Br → I
Atomic size ↑    Shielding ↑    Electronegativity ↓

Important JEE / NEET Concept

Do not say simply that electronegativity decreases because nuclear charge decreases. Nuclear charge actually increases down a group. The better explanation is:

Increase in atomic size + increase in shielding effect → reduced attraction for bonding electrons → decrease in electronegativity.

Periodic Trend

Across a period: Electronegativity ↑

Down a group: Electronegativity ↓

Thus, electronegativity generally increases towards the upper-right of the periodic table.

30 Related MCQs with Solutions

1. Electronegativity decreases down a group mainly because:

A. Nuclear charge decreases

B. Atomic size and shielding increase

C. Number of protons decreases

D. Valence electrons disappear

Answer: B. Atomic size and shielding increase

2. What happens to atomic radius down a group?

A. Decreases

B. Increases

C. Remains constant

D. Becomes zero

Answer: B. Increases

3. The shielding effect down a group generally:

A. Decreases

B. Increases

C. Remains zero

D. Becomes negligible

Answer: B. Increases

4. Which factor reduces the attraction between nucleus and bonding electrons down a group?

A. Decreased distance

B. Increased distance and shielding

C. Decreased shielding

D. Decreased number of shells

Answer: B

5. Correct order of electronegativity in Group 17 is:

A. F < Cl < Br < I

B. F > Cl > Br > I

C. I > Br > Cl > F

D. Cl > F > I > Br

Answer: B. F > Cl > Br > I

6. Which halogen has the highest electronegativity?

A. F

B. Cl

C. Br

D. I

Answer: A. F

7. Moving down a group adds:

A. Proton shells

B. Electron shells

C. Neutron shells

D. Nuclear shells

Answer: B. Electron shells

8. Greater shielding effect causes effective nuclear attraction on valence electrons to:

A. Increase

B. Decrease

C. Remain unchanged

D. Become infinite

Answer: B. Decrease

9. Electronegativity is the tendency to attract:

A. Neutrons

B. Protons

C. Shared bonding electrons

D. Nuclei

Answer: C. Shared bonding electrons

10. Down a group, the distance between nucleus and valence shell:

A. Decreases

B. Increases

C. Remains constant

D. Becomes zero

Answer: B. Increases

11. Which element is more electronegative?

A. Li

B. Na

C. K

D. Rb

Answer: A. Li

12. Which property generally increases down a group?

A. Electronegativity

B. Atomic radius

C. Effective attraction for bonding electrons

D. Non-metallic character

Answer: B. Atomic radius

13. Which combination favours low electronegativity?

A. Small radius + low shielding

B. Large radius + high shielding

C. Small radius + high effective nuclear charge

D. High electron attraction

Answer: B

14. The number of occupied shells down a group:

A. Decreases

B. Increases

C. Remains fixed

D. Becomes one

Answer: B. Increases

15. Which has greater electronegativity?

A. O

B. S

C. Se

D. Te

Answer: A. O

16. Down a group, non-metallic character generally:

A. Increases

B. Decreases

C. Remains constant

D. Doubles

Answer: B. Decreases

17. Which factor increases the distance of valence electrons from the nucleus?

A. Addition of electron shells

B. Decrease in shells

C. Removal of all core electrons

D. Decrease in atomic size

Answer: A

18. Nuclear charge down a group generally:

A. Decreases

B. Increases

C. Remains zero

D. Remains exactly constant

Answer: B. Increases

19. Why does increasing nuclear charge not cause electronegativity to increase down a group?

A. There are no electrons

B. Increased shells and shielding offset the increased nuclear charge

C. Nuclear charge disappears

D. Atomic radius decreases

Answer: B

20. Which has the greatest shielding among these?

A. F

B. Cl

C. Br

D. I

Answer: D. I

21. The effective nuclear attraction experienced by bonding electrons generally decreases down a group because:

A. Atomic radius and shielding increase

B. Atomic radius decreases

C. Shells disappear

D. Nuclear charge becomes zero

Answer: A

22. Which trend is correct?

A. Size ↓, shielding ↓, EN ↑

B. Size ↑, shielding ↑, EN ↓

C. Size ↓, shielding ↑, EN ↓

D. Size ↑, shielding ↓, EN ↑

Answer: B

23. Which element has the highest electronegativity?

A. F

B. Cl

C. Br

D. I

Answer: A. F

24. Electronegativity is generally highest in the:

A. Bottom-left region

B. Top-right region

C. Centre-left region

D. Bottom-right region

Answer: B. Top-right region

25. Down a group, valence electrons experience:

A. Stronger attraction due to smaller size

B. Weaker effective attraction due to distance and shielding

C. No nuclear attraction

D. Only repulsion

Answer: B

26. Which property is responsible for weakening nuclear attraction through inner electrons?

A. Penetration

B. Shielding effect

C. Hybridization

D. Resonance

Answer: B. Shielding effect

27. Which statement is correct?

A. Electronegativity increases down every group

B. Electronegativity generally decreases down a group

C. Atomic radius decreases down a group

D. Shielding decreases down a group

Answer: B

28. Which pair shows the correct relationship?

A. Atomic radius ↑ → Electronegativity ↑

B. Shielding ↑ → Electronegativity ↑

C. Atomic radius ↑ → Electronegativity ↓

D. Shell number ↑ → Electronegativity ↑

Answer: C

29. The best explanation for decreasing electronegativity down a group is:

A. Decreased nuclear charge

B. Increased atomic size and shielding

C. Decreased number of shells

D. Increased electron affinity only

Answer: B

30. Which statement summarizes the trend correctly?

A. Down a group: size ↓, shielding ↓, EN ↑

B. Down a group: size ↑, shielding ↑, EN ↓

C. Down a group: size ↑, shielding ↓, EN ↑

D. Down a group: size ↓, shielding ↑, EN ↓

Answer: B. Size ↑, shielding ↑, EN ↓

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