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Structure of Atom NEET MCQ & Practice Questions

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Structure of Atom Revision Guide for NEET Chemistry

Structure of Atom is part of NEET Chemistry preparation. A strong revision plan should combine concept review with exam-style questions so that definitions, relationships, calculations and exceptions are recalled accurately.

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Important Topics

  • Core definitions and principles
  • Important equations or relationships
  • Common applications and examples
  • Frequently confused concepts
  • Exam-style multiple-choice questions
  • Error review and targeted revision

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What to practise in Structure of Atom

Concept Revision

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Top 20 Structure of Atom MCQs with Answers

These public questions are selected from the exact Structure of Atom chapter, screened for topic relevance and deduplicated so repeated versions of the same MCQ are not shown publicly. Use them for quick revision, then sign in to attempt the complete test experience with more questions, results and performance review.

NEET Chemistry · Structure of Atom · Very Hard

1. For a hydrogen-like species, the electron is in the n = 3 orbit. The magnitude of its energy is proportional to:

  • A. Z²/3²
  • B. Z/3
  • C. 3²/Z²
  • D. Z²/3
Answer: A
Explanation: For a hydrogen-like species, En = −13.6 Z²/n² eV. Therefore the magnitude is proportional to Z²/n².

NEET Chemistry · Structure of Atom · Very Hard

2. The radius of the third Bohr orbit of a hydrogen-like ion with nuclear charge Z = 3, relative to a0, is:

  • A. 9/3
  • B. 3/3
  • C. 3/9
  • D. 93
Answer: A
Explanation: For a hydrogen-like ion, rn = a0 n²/Z. At n = 3, r3/a0 = 9/Z.

NEET Chemistry · Structure of Atom · Very Hard

3. Which transition in a hydrogen atom emits radiation of the shortest wavelength?

  • A. n = 2 to 1
  • B. n = 3 to 2
  • C. n = 4 to 3
  • D. n = 5 to 4
Answer: A
Explanation: Shortest wavelength corresponds to the largest energy difference. Among these transitions, n = 2 to 1 has the greatest energy gap.

NEET Chemistry · Structure of Atom · Very Hard

4. Which set of quantum numbers is not permissible for an electron?

  • A. n = 3, l = 2, m = −2, s = +1/2
  • B. n = 2, l = 2, m = 0, s = −1/2
  • C. n = 4, l = 1, m = 1, s = +1/2
  • D. n = 1, l = 0, m = 0, s = −1/2
Answer: B
Explanation: For a given principal quantum number n, l can have values 0 to n−1. For n = 2, l = 2 is forbidden.

NEET Chemistry · Structure of Atom · Very Hard

5. The maximum number of electrons that can have n = 4 and ml = 0 is:

  • A. 2
  • B. 4
  • C. 8
  • D. 16
Answer: C
Explanation: For n = 4, l = 0, 1, 2, 3 are possible. Each contains one orbital with ml = 0, giving four orbitals and therefore eight electrons.

NEET Chemistry · Structure of Atom · Very Hard

6. How many orbitals in the n = 5 shell have ml = +1?

  • A. 3
  • B. 4
  • C. 5
  • D. 8
Answer: B
Explanation: For n = 5, l = 0 to 4. ml = +1 is possible for l = 1, 2, 3 and 4, giving four orbitals.

NEET Chemistry · Structure of Atom · Very Hard

7. The number of radial nodes in a 5d orbital is:

  • A. 1
  • B. 2
  • C. 3
  • D. 4
Answer: B
Explanation: Radial nodes = n − l − 1 = 5 − 2 − 1 = 2.

NEET Chemistry · Structure of Atom · Very Hard

8. The total number of nodes in a 4p orbital is:

  • A. 1
  • B. 2
  • C. 3
  • D. 4
Answer: C
Explanation: Total nodes = n − 1 = 3. For 4p, one is angular and two are radial.

NEET Chemistry · Structure of Atom · Very Hard

9. Which orbital has zero probability density at the nucleus?

  • A. 1s
  • B. 2s
  • C. 2p
  • D. 3s
Answer: C
Explanation: Only s orbitals have non-zero electron density at the nucleus. A 2p orbital has zero density at r = 0.

NEET Chemistry · Structure of Atom · Very Hard

10. For orbitals of the same principal quantum number in a multi-electron atom, the usual energy order is:

  • A. s < p < d < f
  • B. f < d < p < s
  • C. s = p = d = f
  • D. p < s < f < d
Answer: A
Explanation: Penetration decreases in the order s > p > d > f; greater penetration lowers orbital energy, giving s < p < d < f.

NEET Chemistry · Structure of Atom · Very Hard

11. According to the (n + l) rule, which orbital is filled first?

  • A. 4s
  • B. 3d
  • C. 4p
  • D. 5s
Answer: A
Explanation: For 4s, n+l = 4; for 3d, n+l = 5; for 4p, 5; for 5s, 5. The lowest n+l orbital fills first.

NEET Chemistry · Structure of Atom · Very Hard

12. The ground-state electronic configuration of chromium is:

  • A. [Ar] 3d4 4s2
  • B. [Ar] 3d5 4s1
  • C. [Ar] 3d6
  • D. [Ar] 3d3 4s3
Answer: B
Explanation: Chromium adopts [Ar] 3d5 4s1 because the half-filled d subshell has enhanced stability.

NEET Chemistry · Structure of Atom · Very Hard

13. Which species has the maximum number of unpaired electrons?

  • A. Fe2+
  • B. Mn2+
  • C. Co2+
  • D. Ni2+
Answer: B
Explanation: Mn2+ has configuration [Ar] 3d5 and therefore five unpaired electrons.

NEET Chemistry · Structure of Atom · Very Hard

14. Which electronic configuration violates the Pauli exclusion principle?

  • A. Two electrons in one orbital with opposite spins
  • B. Two electrons in one orbital with parallel spins
  • C. One electron in each of three degenerate orbitals
  • D. A filled 1s orbital
Answer: B
Explanation: Two electrons occupying the same orbital must have opposite spins. Parallel spins in one orbital violate Pauli's principle.

NEET Chemistry · Structure of Atom · Very Hard

15. Hund's rule predicts that three electrons entering three degenerate p orbitals will:

  • A. Pair in one orbital first
  • B. Occupy separate orbitals with parallel spins
  • C. Occupy separate orbitals with opposite spins
  • D. Leave one orbital doubly occupied and one empty
Answer: B
Explanation: Electrons occupy degenerate orbitals singly with parallel spins before pairing.

NEET Chemistry · Structure of Atom · Very Hard

16. If the uncertainty in position of an electron is reduced by a factor of two, the minimum uncertainty in momentum:

  • A. Is halved
  • B. Is doubled
  • C. Remains unchanged
  • D. Becomes four times
Answer: B
Explanation: From ΔxΔp ≥ h/4π, reducing Δx by two requires the minimum Δp to double.

NEET Chemistry · Structure of Atom · Very Hard

17. The de Broglie wavelength of a particle is inversely proportional to:

  • A. Its kinetic energy
  • B. Its momentum
  • C. Its charge
  • D. Its potential energy
Answer: B
Explanation: The de Broglie relation is λ = h/p, so wavelength is inversely proportional to momentum.

NEET Chemistry · Structure of Atom · Very Hard

18. An electron and a proton have the same de Broglie wavelength. They must have the same:

  • A. Velocity
  • B. Kinetic energy
  • C. Momentum
  • D. Acceleration
Answer: C
Explanation: Since λ = h/p, equal wavelength implies equal momentum.

NEET Chemistry · Structure of Atom · Very Hard

19. The photoelectric effect directly supports the:

  • A. Wave nature of electrons
  • B. Particle nature of light
  • C. Nuclear model of atom
  • D. Quantisation of angular momentum only
Answer: B
Explanation: The photoelectric effect is explained by photons carrying discrete packets of energy, demonstrating the particle nature of light.

NEET Chemistry · Structure of Atom · Very Hard

20. When the frequency of incident radiation exceeds the threshold frequency, increasing intensity primarily increases the:

  • A. Maximum kinetic energy of photoelectrons
  • B. Number of emitted photoelectrons
  • C. Threshold frequency
  • D. Work function
Answer: B
Explanation: At fixed frequency above threshold, intensity controls photon flux and therefore the number of photoelectrons, not their maximum kinetic energy.

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Structure of Atom Practice Tests

Structure of Atom Frequently Asked Questions

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