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NEET Chemistry: Bohr model of a hydrogen atom Practice Questions

15 free multiple-choice questions on Bohr model of a hydrogen atom (Atomic Structure) for NEET Chemistry, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.

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  1. Q1. The allowed stationary states for an electron in a hydrogen atom are defined by specific principal quantum numbers (n). Which of the following is the correct value for the minimum principal quantum number (n)?

    • A2
    • B1
    • C3
    • D0
    Show answer & explanation

    Correct answer: B — 1

    For a stable orbit (stationary state) in the Bohr model of the hydrogen atom, the principal quantum number (n) must be a positive integer, meaning the minimum allowed value is 1.

  2. Q2. Which of the following statements is a fundamental postulate of the Bohr model for the hydrogen atom?

    • AElectrons revolve only in circular orbits, not elliptical ones.
    • BThe radius of the orbit is determined by the uncertainty principle.
    • CThe angular momentum of the electron is quantized.
    • DThe energy of the electron is continuously variable.
    Show answer & explanation

    Correct answer: C — The angular momentum of the electron is quantized.

    The Bohr model postulates that the angular momentum of the electron is quantized (i.e., it can only take discrete values mvr = nħ), which leads to quantized energy levels.

  3. Q3. The electron in the ground state of a hydrogen atom has which value for the principal quantum number n?

    • An=2
    • Bn=3
    • Cn=1
    • Dn=0
    Show answer & explanation

    Correct answer: C — n=1

    The ground state corresponds to the lowest possible energy level, which is defined by the principal quantum number n=1.

  4. Q4. Which quantity is quantized in the Bohr model for the electron revolving around the nucleus of a hydrogen atom?

    • Aangular momentum
    • Bradial distance
    • Ctotal energy
    • Dvelocity of the electron
    Show answer & explanation

    Correct answer: A — angular momentum

    In the Bohr model, the angular momentum of the electron is quantized, taking discrete values based on the principal quantum number n (L = nħ).

  5. Q5. Which of the following statements is true regarding the allowed stationary states in the Bohr model for a hydrogen atom?

    • AThe energy of the electron is independent of the principal quantum number n.
    • BThe total energy of the electron is continuously variable.
    • CThe radius of the orbit depends only on the mass of the electron.
    • DThe angular momentum of the electron is quantized and exists only in discrete values.
    Show answer & explanation

    Correct answer: D — The angular momentum of the electron is quantized and exists only in discrete values.

    According to the Bohr model, the angular momentum of the electron is quantized, meaning it can only exist in discrete, specific values (L=nħ), which dictates the allowed stationary states.

  6. Q6. Which condition must be satisfied for an electron to exist in a stable orbit according to the Bohr model?

    • AThe angular momentum must be quantized.
    • BThe orbital velocity must be constant.
    • CThe total energy must be maximum.
    • DThe angular momentum must be zero.
    Show answer & explanation

    Correct answer: A — The angular momentum must be quantized.

    In the Bohr model, only certain discrete, quantized values of angular momentum are allowed for the electron to exist in stable, stationary orbits.

  7. Q7. According to the Bohr model, the radius of the orbit for an electron in the n-th stationary state is related to n by which formula?

    • Ar = 1/n
    • Br = n² a₀
    • Cr = nħ
    • Dr = n/a₀
    Show answer & explanation

    Correct answer: D — r = n/a₀

    The radius of the orbit is given by rₙ = n² a₀, where a₀ is the Bohr radius. The question asks for the relationship defining the radius for a given state.

  8. Q8. The radius of the orbit for a given principal quantum number n in the Bohr model is inversely proportional to which quantity?

    • AThe angular momentum.
    • BThe speed of the electron.
    • CThe principal quantum number n.
    • DThe mass of the electron.
    Show answer & explanation

    Correct answer: C — The principal quantum number n.

    The radius of the orbit (rₙ) is inversely proportional to the principal quantum number n.

  9. Q9. In the Bohr model for the hydrogen atom, the allowed stationary orbits for the electron are defined by which condition?

    • AThe quantization of angular momentum
    • BThe quantization of energy
    • CThe total angular momentum
    • DThe total energy of the system
    Show answer & explanation

    Correct answer: B — The quantization of energy

    The Bohr model postulates that the angular momentum of the electron must be quantized, which leads to discrete, stable orbits (stationary states).

  10. Q10. In the context of the Bohr model, what defines a stationary state for an electron in a hydrogen atom?

    • AThe electron has zero kinetic energy.
    • BThe electron's energy is independent of its position.
    • CThe electron's angular momentum is constant.
    • DThe electron is moving at a constant velocity.
    Show answer & explanation

    Correct answer: C — The electron's angular momentum is constant.

    A stationary state is defined by the condition that the angular momentum of the electron is quantized and constant, which corresponds to a stable orbit.

  11. Q11. Which of the following is a fundamental postulate of the Bohr model for the hydrogen atom?

    • AQuantization of energy
    • BQuantization of the orbit
    • CQuantization of angular momentum
    • DQuantization of the radius
    Show answer & explanation

    Correct answer: C — Quantization of angular momentum

    The Bohr model is fundamentally based on the quantization of angular momentum (L = nħ) and energy (Eₙ = -13.6/n² for hydrogen).

  12. Q12. The energy levels in the Bohr model are directly proportional to which quantity?

    • AThe radius of the orbit.
    • BThe speed of light.
    • CThe principal quantum number n.
    • DThe mass of the nucleus.
    Show answer & explanation

    Correct answer: C — The principal quantum number n.

    The allowed energy levels (Eₙ) in the Bohr model are directly proportional to the principal quantum number n.

  13. Q13. Which statement accurately describes the quantization of orbits in the Bohr model?

    • AThe angular momentum of the electron is directly proportional to its energy.
    • BThe radius is inversely proportional to the principal quantum number.
    • CElectrons can exist in any radius around the nucleus.
    • DOnly orbits with integer values of n are permitted.
    Show answer & explanation

    Correct answer: D — Only orbits with integer values of n are permitted.

    The Bohr model postulates that only orbits corresponding to integer values of the principal quantum number (n=1, 2, 3, ...) are allowed, leading to quantized orbits.

  14. Q14. Which of the following transitions corresponds to the emission of a photon in the Balmer series for the hydrogen atom?

    • An=1 to n=2
    • Bn=4 to n=2
    • Cn=2 to n=1
    • Dn=3 to n=1
    Show answer & explanation

    Correct answer: A — n=1 to n=2

    The Balmer series corresponds to transitions where the final energy level (n_f) is 2. Therefore, the transitions are nᵢ → 2, where nᵢ > 2. The lowest transition for the Balmer series is n=3 → 2. (Note: Option 0 represents the sequence of transitions leading to the series, focusing on the final state n=2.)

  15. Q15. If an electron is in a higher energy level (n₂) in a hydrogen atom, the energy of the system is related to the change in energy. How is the energy of an electron in a specific orbit calculated in the Bohr model?

    • AE = 1/2 m v²
    • BE = n h ν
    • CE = -R_H n²/n²
    • DE = -13.6/n²
    Show answer & explanation

    Correct answer: D — E = -13.6/n²

    The total energy of an electron in the nth orbit of a hydrogen atom is given by the formula Eₙ = -13.6/n² (where 13.6 corresponds to R_H in eV or Joules).

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