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Structure of an Atom WBJEE MCQ & Practice Questions

Practice Structure of an Atom MCQs for WBJEE Chemistry with answers, explanations, chapter revision and related ChemNexa mock tests.

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Structure of an Atom Revision Guide for WBJEE Chemistry

Structure of an Atom is part of WBJEE 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 an Atom

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Top 20 Structure of an Atom MCQs with Answers

These public questions are selected from the exact Structure of an 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.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

1. The maximum number of electrons in a shell with principal quantum number n is

  • A. 2n
  • B. 4n^2
  • C. 2n^2
  • D. n^2
Answer: C
Explanation: The shell capacity is 2n².

WBJEE Chemistry · Structure of an Atom · Very Very Hard

2. For an orbital, the azimuthal quantum number l determines its

  • A. Nuclear charge
  • B. Shape/subshell
  • C. Size only
  • D. Spin
Answer: B
Explanation: l identifies the subshell and orbital shape.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

3. For a p subshell, l equals

  • A. 1
  • B. 0
  • C. 2
  • D. 3
Answer: A
Explanation: p corresponds to l=1.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

4. For a d subshell, the number of orbitals is

  • A. 3
  • B. 7
  • C. 1
  • D. 5
Answer: D
Explanation: m_l ranges from -2 to +2, giving five orbitals.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

5. The magnetic quantum number specifies

  • A. Shell energy only
  • B. Atomic mass
  • C. Orientation of an orbital
  • D. Electron spin only
Answer: C
Explanation: m_l labels orbital orientations.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

6. Electron spin quantum number can have values

  • A. Only +1/2
  • B. +1/2 or -1/2
  • C. 0 or 1
  • D. -1,0,+1
Answer: B
Explanation: An electron has two allowed spin projections.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

7. Pauli exclusion principle states that two electrons in an atom cannot have

  • A. All four quantum numbers identical
  • B. The same n value
  • C. The same spin always
  • D. The same l value
Answer: A
Explanation: No two electrons in an atom can share all four quantum numbers.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

8. Hund's rule favours

  • A. Immediate pairing in one orbital
  • B. Empty lower orbitals
  • C. Opposite spins in separate shells
  • D. Maximum number of unpaired electrons in degenerate orbitals
Answer: D
Explanation: Degenerate orbitals are singly occupied with parallel spins before pairing.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

9. Aufbau principle fills orbitals approximately in order of

  • A. Decreasing n only
  • B. Atomic mass
  • C. Increasing energy
  • D. Increasing size only
Answer: C
Explanation: Electrons occupy lower-energy orbitals first.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

10. According to the (n+l) rule, the orbital with smaller n+l is generally

  • A. Forbidden
  • B. Lower in energy
  • C. Higher in energy
  • D. Always degenerate
Answer: B
Explanation: The Madelung rule orders orbital energies using n+l.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

11. The ground-state configuration of Cr shows an exception commonly written as

  • A. [Ar] 3d5 4s1
  • B. [Ar] 3d4 4s2
  • C. [Ar] 3d6
  • D. [Ar] 4s2 4p4
Answer: A
Explanation: Half-filled d5 stability leads to 3d5 4s1.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

12. The ground-state configuration of Cu is commonly

  • A. [Ar] 3d9 4s2
  • B. [Ar] 3d8 4s3
  • C. [Ar] 4s2 4p9
  • D. [Ar] 3d10 4s1
Answer: D
Explanation: Filled 3d10 gives the observed configuration.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

13. de Broglie wavelength is inversely proportional to

  • A. Velocity only
  • B. Charge
  • C. Momentum
  • D. Mass only
Answer: C
Explanation: λ=h/p.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

14. The de Broglie relation is

  • A. λ = hc
  • B. λ = h/p
  • C. λ = hp
  • D. λ = p/h
Answer: B
Explanation: Matter-wave wavelength equals Planck constant divided by momentum.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

15. Heisenberg uncertainty principle relates uncertainties in

  • A. Position and momentum
  • B. Mass and charge
  • C. Atomic number and mass
  • D. Spin and charge only
Answer: A
Explanation: ΔxΔp has a lower quantum limit.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

16. A photon has energy

  • A. E=h/ν
  • B. E=ν/h
  • C. E=mc only
  • D. E=hν
Answer: D
Explanation: Planck's relation gives photon energy E=hν.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

17. For electromagnetic radiation in vacuum

  • A. c=λ/ν
  • B. c=hν
  • C. c=νλ
  • D. c=ν/λ
Answer: C
Explanation: Wave speed equals frequency times wavelength.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

18. Increasing frequency of radiation causes photon energy to

  • A. Become zero
  • B. Increase
  • C. Decrease
  • D. Remain constant
Answer: B
Explanation: E=hν.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

19. The photoelectric effect supports the

  • A. Particle nature of light
  • B. Only wave nature of matter
  • C. Nuclear model only
  • D. Existence of neutrons
Answer: A
Explanation: Energy exchange occurs in photons.

WBJEE Chemistry · Structure of an Atom · Very Very Hard

20. The threshold frequency is the minimum frequency needed to

  • A. Produce diffraction
  • B. Create neutrons
  • C. Ionise every gas
  • D. Eject photoelectrons from a surface
Answer: D
Explanation: Below threshold frequency photoemission does not occur.

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Structure of an Atom Practice Tests

Structure of an Atom Frequently Asked Questions

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