Covalent Bonding – Concept of electronegativity: NEET MCQs with Answers

15 free questions on Covalent Bonding – Concept of electronegativity for NEET (UG), starting with previous-year NEET and AIPMT questions. Try each one, then tap Show answer for the answer and a short explanation.

Syllabus covered: Concept of electronegativity. Fajan’s rule, dipole moment: Valence Shell Electron Pair Repulsion (VSEPR ) theory and shapes of simple molecules.

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Question 1

Previous-year question
What are the correct shape and hybridisation of BrF₅? [NEET 2024 (Sawaimadhopur)]
  1. Square pyramidal and d²sp³
  2. Trigonal bipyramidal and sp³d²
  3. Trigonal bipyramidal and d²sp³
  4. Square pyramidal and sp³d²
Show answer
Answer: (D) Square pyramidal and sp³d²
Explanation: In BrF₅, Br has 5 bond pairs and 1 lone pair (6 electron pairs), so it uses sp³d² hybridisation (outer d orbitals). The octahedral electron geometry with one position occupied by a lone pair gives a square pyramidal shape. d²sp³ (inner d orbitals) is not possible for Br, and trigonal bipyramidal corresponds to 5 electron pairs.

Question 2

Previous-year question
Arrange the following hydrides in decreasing order of bond angle and choose the correct answer. [NEET 2024 (Sawaimadhopur)]
A. SbH₃
B. AsH₃
C. PH₃
D. NH₃
  1. B > A > C > D
  2. D > C > B > A
  3. A > C > B > D
  4. B > A > D > C
Show answer
Answer: (B) D > C > B > A
Explanation: Down group 15 the electronegativity of the central atom decreases, so bonding pairs lie farther from it and bond-pair repulsion falls; the bond angle therefore decreases: NH₃ (107.8°) > PH₃ (93.6°) > AsH₃ (91.8°) > SbH₃ (91.3°), i.e. D > C > B > A.

Question 3

Previous-year question
Which pair of compounds has exactly one lone pair of electrons on the central atom in each member? [NEET 2024 (Sawaimadhopur)]
  1. SF₄, ClF₃
  2. ClF₃, XeF₄
  3. XeF₄, BrF₅
  4. SF₄, BrF₅
Show answer
Answer: (D) SF₄, BrF₅
Explanation: SF₄ (4 bp + 1 lp, see-saw) and BrF₅ (5 bp + 1 lp, square pyramidal) each have one lone pair on the central atom. ClF₃ and XeF₄ each have two lone pairs, so the other pairs are ruled out.

Question 4

Previous-year question
Find the pair in which the molecule is wrongly matched with its shape (geometry). [NEET 2020 (COVID-19)]
  1. PCl₅ – Trigonal planar
  2. SF₆ – Octahedral
  3. BeCl₂ – Linear
  4. NH₃ – Trigonal pyramidal
Show answer
Answer: (A) PCl₅ – Trigonal planar
Explanation: PCl₅ has five bond pairs around phosphorus (sp³d) and is trigonal bipyramidal, not trigonal planar, so this pair is wrongly matched. SF₆ (sp³d²) is octahedral, BeCl₂ (sp) is linear and NH₃ (3 bp + 1 lp) is trigonal pyramidal, all correctly matched.

Question 5

Previous-year question
Identify which of the following orders are correct for the property mentioned against each, and choose the correct answer. [NEET 2025]
(A) H₂O > NH₃ > CHCl₃ — dipole moment
(B) XeF₄ > XeO₃ > XeF₂ — number of lone pairs on the central atom
(C) O–H > C–H > N–O — bond length
(D) N₂ > O₂ > H₂ — bond enthalpy
  1. A, D only
  2. B, D only
  3. A, C only
  4. B, C only
Show answer
Answer: (A) A, D only
Explanation: A is correct: dipole moments are H₂O (1.85 D) > NH₃ (1.47 D) > CHCl₃ (≈ 1.0 D). D is correct: bond enthalpies are N₂ (946) > O₂ (498) > H₂ (435.8 kJ mol⁻¹). B is wrong because lone pairs on Xe are XeF₂ (3) > XeF₄ (2) > XeO₃ (1); C is wrong because bond lengths are N–O (136 pm) > C–H (107 pm) > O–H (96 pm).

Question 6

Previous-year question
Which of the following bonds has the greatest bond length? [NEET 2021 (Paper-2)]
  1. P – O
  2. S – O
  3. Cl – O
  4. O = O
Show answer
Answer: (A) P – O
Explanation: Bond length increases with the size of the bonded atoms. Atomic size decreases across period 3 (P > S > Cl), so the P–O bond is the longest of the three single bonds. The O=O bond is a double bond between two small atoms and is the shortest.

Question 7

Previous-year question
Which of the following molecules has the maximum dipole moment? [AIPMT 2014]
  1. CO₂
  2. CH₄
  3. NH₃
  4. NF₃
Show answer
Answer: (C) NH₃
Explanation: CO₂ (linear) and CH₄ (tetrahedral) are symmetrical, so their bond dipoles cancel and μ = 0. In NH₃ the lone pair dipole points in the same direction as the resultant of the three N–H bond dipoles, so they reinforce; in NF₃ the highly electronegative fluorines pull the bond dipoles opposite to the lone pair dipole and largely cancel it. Hence NH₃ has the maximum dipole moment.
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Question 8

Which pair consists of species whose central atoms have different hybridisations but the same bond angle?
  1. CH₄ and NH₄⁺
  2. BeCl₂ and XeF₂
  3. BF₃ and NO₃⁻
  4. NH₃ and H₂O
Show answer
Answer: (B) BeCl₂ and XeF₂
Explanation: Be in BeCl₂ is sp hybridised and Xe in XeF₂ is sp³d hybridised, yet both molecules are linear with a 180° bond angle. BF₃ and NO₃⁻ share sp² and 120°, and CH₄ and NH₄⁺ share sp³ and 109.5°. NH₃ and H₂O are both sp³ but have different angles.

Question 9

Which statement about the dipole moment of a water molecule is correct?
  1. It is about 1.85 D because the bent shape leaves the two O–H bond moments only partly cancelled
  2. It is smaller than the dipole moment of H₂S
  3. It is zero because oxygen carries two lone pairs
  4. It is zero because the two O–H bond moments cancel each other
Show answer
Answer: (A) It is about 1.85 D because the bent shape leaves the two O–H bond moments only partly cancelled
Explanation: The water molecule is bent with an angle of about 104.5°, so the two O–H bond moments add to a resultant instead of cancelling. The measured value is about 1.85 D. Since oxygen is more electronegative than sulphur, H₂O is more polar than H₂S.

Question 10

Which is the correct decreasing order of dipole moment for H₂O, HCl, NF₃ and CO₂?
  1. NF₃ > H₂O > HCl > CO₂
  2. H₂O > HCl > NF₃ > CO₂
  3. CO₂ > NF₃ > HCl > H₂O
  4. HCl > H₂O > CO₂ > NF₃
Show answer
Answer: (B) H₂O > HCl > NF₃ > CO₂
Explanation: Bent H₂O has a large dipole moment of about 1.85 D, and HCl is about 1.03 D. In NF₃ the lone-pair moment opposes the N–F bond moments, leaving only about 0.23 D. Linear CO₂ has zero dipole moment because its two bond moments cancel.

Question 11

How many of the following species have all their bond angles equal to 120°? BF₃, NO₃⁻, CH₃⁺, SO₃, NH₃, ClF₃
  1. 4
  2. 5
  3. 3
  4. 2
Show answer
Answer: (A) 4
Explanation: BF₃, NO₃⁻, CH₃⁺ and SO₃ have three bond pairs and no lone pair on the central atom, giving trigonal planar shapes with 120° angles. NH₃ is pyramidal with angles near 107°, and ClF₃ is T-shaped with angles below 90°. So four species qualify.

Question 12

Xenon in XeO₂F₂ has five electron domains arranged in a trigonal bipyramid. According to VSEPR theory, which arrangement of the two oxygen atoms, the two fluorine atoms and the lone pair around xenon is correct?
  1. Both O atoms axial; both F atoms and the lone pair equatorial
  2. Both F atoms axial; both O atoms and the lone pair equatorial
  3. The lone pair and one F atom axial; both O atoms and the other F atom equatorial
  4. One O atom and one F atom axial; the other O atom, the other F atom and the lone pair equatorial
Show answer
Answer: (B) Both F atoms axial; both O atoms and the lone pair equatorial
Explanation: Equatorial positions are less crowded (120° to two neighbours) than axial ones, so the lone pair and the bulky, multiply bonded oxygen atoms take equatorial positions. The more electronegative fluorine atoms occupy the two axial positions. This gives XeO₂F₂ its see-saw shape.

Question 13

The polarity of the HF molecule is shown by a crossed arrow placed on its Lewis structure. Which description of this arrow is correct?
  1. The cross is on H and the arrowhead on F, showing the shift of electron density; it is opposite to the conventional dipole moment vector
  2. The cross is on F and the arrowhead on H, and the arrow runs opposite to the conventional dipole moment vector
  3. The cross is on F and the arrowhead on H, showing the shift of electron density towards H
  4. The cross is on H and the arrowhead on F, and the arrow runs in the same direction as the conventional dipole moment vector
Show answer
Answer: (A) The cross is on H and the arrowhead on F, showing the shift of electron density; it is opposite to the conventional dipole moment vector
Explanation: The cross marks the positive end and the arrowhead marks the negative end, so in HF the cross is on hydrogen and the head on fluorine. The arrow shows the shift of electron density towards the more electronegative fluorine. The conventional dipole moment vector has its tail on the negative centre and its head on the positive centre, so the crossed arrow runs the opposite way.

Question 14

A diatomic molecule has a bond length of 1.50 Å, and its ends carry partial charges of +0.20e and −0.20e. What is its dipole moment in SI units and in debye? (e = 1.6 × 10⁻¹⁹ C; 1 D = 3.34 × 10⁻³⁰ C m)
  1. 4.8 × 10⁻³⁰ C m, or about 16 D
  2. 2.4 × 10⁻²⁹ C m, or about 7.2 D
  3. 4.8 × 10⁻³⁰ C m, or about 1.44 D
  4. 3.2 × 10⁻²⁰ C m, or about 1.0 D
Show answer
Answer: (C) 4.8 × 10⁻³⁰ C m, or about 1.44 D
Explanation: Dipole moment is charge multiplied by the distance between the charges, and its SI unit is the coulomb metre. Here μ = 0.20 × 1.6 × 10⁻¹⁹ C × 1.50 × 10⁻¹⁰ m = 4.8 × 10⁻³⁰ C m. Dividing by 3.34 × 10⁻³⁰ C m per debye gives about 1.44 D.

Question 15

Which comparison of the hydronium ion, H₃O⁺, with the water molecule is correct?
  1. H₃O⁺ is bent like water with two lone pairs on oxygen, and its H–O–H angle is smaller than in water
  2. H₃O⁺ is trigonal pyramidal with one lone pair on oxygen, and its H–O–H angle is larger than in water
  3. H₃O⁺ is tetrahedral with no lone pair on oxygen, and its bond angle is exactly 109.5°
  4. H₃O⁺ is trigonal planar with sp² oxygen, and its bond angle is 120°
Show answer
Answer: (B) H₃O⁺ is trigonal pyramidal with one lone pair on oxygen, and its H–O–H angle is larger than in water
Explanation: When water accepts a proton, one of the two lone pairs on oxygen becomes a bond pair. Oxygen keeps four electron pairs and sp³ hybridisation, now with three bond pairs and one lone pair, so the ion is trigonal pyramidal like NH₃. With only one lone pair, lone pair repulsion is weaker than in water, so the bond angle is larger than 104.5°.

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