“Bohr’s Model” MCQ with Answer Explanation.

31. Which energy level in a hydrogen atom corresponds to the electron being completely removed?

A) n=1
B) n=0
C) n=∞
D) n=2

Answer: C) n=∞.

Explanation: An electron is considered to be completely removed when it reaches an infinite energy level, indicating it is no longer bound to the atom.

32. What happens to the energy of the electron as it moves from n=1 to n=3?

A) It increases.
B) It decreases.
C) It remains the same.
D) It becomes zero.

Answer: A) It increases.

Explanation: Moving to a higher energy level (n=3) requires the electron to absorb energy.

33. Which physical constant relates the frequency of emitted light to the energy change in the electron?

A) Gravitational constant
B) Planck constant
C) Boltzmann constant
D) Speed of light

Answer: B) Planck constant.

Explanation: The Planck constant connects energy and frequency, described by the equation E = hf, where h is the Planck constant and f is frequency.

34. In Bohr’s model, which force keeps the electrons in orbit around the nucleus?

A) Gravitational force
B) Magnetic force
C) Electrostatic force
D) Nuclear force

Answer: C) Electrostatic force.

Explanation: The electrostatic attraction between the negatively charged electrons and the positively charged nucleus is what keeps electrons in orbit.

35. In the Bohr model, which quantum number is associated with the shape of the electron orbit?

A) Principal quantum number (n)
B) Azimuthal quantum number (l)
C) Magnetic quantum number (m)
D) Spin quantum number (s)

Answer: B) Azimuthal quantum number (l).

Explanation: The azimuthal quantum number (l) describes the shape of the orbitals, while the principal quantum number (n) describes their size and energy.

36. Which of the following correctly describes the transition of an electron in a hydrogen atom from n=3 to n=2?

A) It emits energy as a photon.
B) It absorbs energy as a photon.
C) It does not change energy levels.
D) It leads to ionization.

Answer: A) It emits energy as a photon.

Explanation: This transition releases energy in the form of a photon as the electron moves to a lower energy level.

37. The first ionization energy of hydrogen is:

A) 13.6 eV
B) 1.51 eV
C) 3.4 eV
D) 0 eV

Answer: A) 13.6 eV.

Explanation: The first ionization energy is equivalent to the energy required to remove the electron from the ground state (n=1) of hydrogen.

38. What is the main purpose of the Bohr model in atomic theory?

A) To explain chemical bonding.
B) To describe electron orbits and energy levels.
C) To define atomic mass.
D) To explain nuclear reactions.

Answer: B) To describe electron orbits and energy levels.

Explanation: The Bohr model primarily aims to explain the arrangement of electrons and their energy states in atoms.

39. In Bohr’s model, which of the following is true about the energy of electrons in higher orbits?

A) It is less than that in lower orbits.
B) It is equal to that in lower orbits.
C) It is greater than that in lower orbits.
D) It is negative.

Answer: C) It is greater than that in lower orbits.

Explanation: Higher orbits correspond to higher energy levels; thus, the energy of electrons increases as they move to higher orbits.

40. What type of light is emitted when an electron transitions from n=4 to n=3?

A) Ultraviolet light
B) Visible light
C) Infrared light
D) X-rays

Answer: C) Infrared light.

Explanation: Transitions involving smaller energy differences, such as from n=4 to n=3, typically emit infrared light.