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NEET Physics: Bohr model and energy levels Practice Questions

15 free multiple-choice questions on Bohr model and energy levels (Atoms and Nuclei) for NEET Physics, 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. Which of the following statements is a fundamental postulate of the Bohr model?

    • AThe velocity of the electron is constant.
    • BThe energy of the system is continuous.
    • CThe angular momentum of the electron is quantized.
    • DThe electron moves in a classical orbit.
    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, meaning it can only exist in discrete, specific values.

  2. Q2. Which of the following describes the transition of an electron between two stationary energy levels in the Bohr model?

    • AThe electron remains in the same state without energy change.
    • BThe electron changes its orbital radius instantaneously.
    • CThe electron emits a photon.
    • DThe electron absorbs energy.
    Show answer & explanation

    Correct answer: C — The electron emits a photon.

    When an electron moves from a higher energy level to a lower energy level, it releases the energy difference in the form of electromagnetic radiation (a photon).

  3. Q3. In the Bohr model of the hydrogen atom, the energy of an electron in the n⁽th) stationary orbit is proportional to which expression?

    • A1/n²
    • B1/n
    • Cn
    • Dn²
    Show answer & explanation

    Correct answer: A — 1/n²

    The energy of an electron in the n⁽th) orbit of a hydrogen atom is given by the formula Eₙ = -R_H/n², where R_H is the Rydberg constant. Thus, the energy is inversely proportional to the square of the principal quantum number (Eₙ ∝ 1/n²).

  4. Q4. For the hydrogen atom, the radius of the n-th orbit in the Bohr model is proportional to which term?

    • An²
    • B1/n²
    • C1/n
    • Dn
    Show answer & explanation

    Correct answer: B — 1/n²

    The radius of the n-th orbit is given by rₙ ∝ n², where n is the principal quantum number.

  5. Q5. What is the term used to describe the minimum possible energy state of an electron in an atomic system?

    • ATransition state.
    • BMaximum energy state.
    • CExcited state.
    • DGround state.
    Show answer & explanation

    Correct answer: D — Ground state.

    The minimum possible energy state of an electron in an atom is defined as the ground state.

  6. Q6. The radius of the nth orbit in the Bohr model is inversely proportional to which term?

    • AThe total energy of the system.
    • BThe charge of the nucleus Z.
    • 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 proportional to n², meaning it is inversely related to the quantization number n in a conceptual sense of determining the size of the orbit.

  7. Q7. The Bohr model successfully explained the stability of the atom primarily by introducing which concept?

    • AQuantization of angular momentum.
    • BHeisenberg's Uncertainty Principle.
    • CRelativistic effects of the electron motion.
    • DThe concept of continuous wave function.
    Show answer & explanation

    Correct answer: A — Quantization of angular momentum.

    The quantization of angular momentum ensures that electrons remain in stable, well-defined orbits, thus explaining the stability of the atom in this model.

  8. Q8. What is the primary postulate of the Bohr model concerning the electron's motion in an orbit?

    • AThe electron follows classical mechanics in the orbit
    • BThe electron has only discrete, stationary orbits
    • CThe electron moves randomly in the orbit
    • DThe electron can exist at any radius
    Show answer & explanation

    Correct answer: B — The electron has only discrete, stationary orbits

    The core postulate of the Bohr model is that the electron exists only in specific, quantized, stationary orbits, and these orbits are allowed states.

  9. Q9. In the Bohr model, what physical quantity determines the allowed stationary energy levels of an electron around a nucleus?

    • AThe spin of the electron only.
    • BThe total kinetic energy.
    • CThe principal quantum number (n).
    • DThe electron's speed.
    Show answer & explanation

    Correct answer: C — The principal quantum number (n).

    The allowed stationary energy levels in the Bohr model are determined solely by the principal quantum number (n).

  10. Q10. If an electron moves in a stable circular orbit around a nucleus, the change in its orbital angular momentum must be related to:

    • AThe classical kinetic energy.
    • BThe total energy of the system.
    • CThe quantization of angular momentum.
    • DThe change in potential energy.
    Show answer & explanation

    Correct answer: C — The quantization of angular momentum.

    A core principle of the Bohr model is that the angular momentum (L) of the electron is quantized, meaning it takes only discrete values.

  11. Q11. Which of the following statements is a postulate of the Bohr model regarding the electron's motion in an orbit?

    • AThe electron moves in a classical orbit
    • BThe electron moves in a stationary orbit with discrete energy levels
    • CThe electron can transition between any energy levels without absorbing energy
    • DThe electron can exist in any orbit
    Show answer & explanation

    Correct answer: B — The electron moves in a stationary orbit with discrete energy levels

    The Bohr model postulates that electrons revolve around the nucleus only in specific, stationary orbits (stationary states) with discrete, quantized energy levels.

  12. Q12. In the Bohr model, the radius of the orbit of an electron in a hydrogen-like atom is inversely proportional to which of the following quantities?

    • AThe principal quantum number (n)
    • BThe energy of the orbit (E)
    • CThe speed of the electron (v)
    • DThe mass of the electron (m)
    Show answer & explanation

    Correct answer: A — The principal quantum number (n)

    According to the Bohr model, the radius (rₙ) of the orbit for an electron is inversely proportional to the square of the principal quantum number (n²). This means that as the principal quantum number increases, the radius of the orbit increases.

  13. Q13. The principal quantum number (n) in the Bohr model determines which of the following properties of the electron orbital?

    • AThe size of the orbit (radius)
    • BThe total energy of the electron
    • CThe exact wavelength of emitted radiation
    • DThe magnetic moment of the electron
    Show answer & explanation

    Correct answer: A — The size of the orbit (radius)

    The principal quantum number (n) defines the allowed stationary states and directly determines the size of the allowed orbits (the radius of the orbit) for an electron in a hydrogen-like atom.

  14. Q14. In the Bohr model, the angular momentum of the electron is quantized. What is the condition for the allowed stationary orbits?

    • AThe angular momentum must be an integer multiple of h/2ζ.
    • BThe total energy must be inversely proportional to the square of the radius.
    • CThe radius of the orbit must be an integer multiple of the Bohr radius.
    • DThe total energy must be an integer multiple of hζ.
    Show answer & explanation

    Correct answer: A — The angular momentum must be an integer multiple of h/2ζ.

    According to the Bohr model, for a stable orbit to exist, the angular momentum of the electron must be quantized, given by L = mvr = nh/2π, where n is an integer. This condition ensures that only discrete energy levels are allowed.

  15. Q15. The energy of an electron in the nth orbit of a hydrogen atom is given by the formula Eₙ = -13.6/n² (in eV). What does this formula fundamentally demonstrate?

    • AThe angular momentum is linearly related to n.
    • BThe energy levels are discrete (quantized).
    • CThe kinetic energy is zero for all orbits.
    • DThe energy is inversely proportional to the radius.
    Show answer & explanation

    Correct answer: B — The energy levels are discrete (quantized).

    The inverse square dependence on n² shows that the energy levels are discrete (quantized) and non-uniformly spaced.

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