- What is the significance of the constant ‘h’ in the Bohr model?
A) It represents energy.
B) It is the Planck constant.
C) It is the mass of an electron.
D) It measures the speed of light.
Answer: B) It is the Planck constant.
Explanation: The Planck constant (h) is crucial in quantum mechanics, linking energy and frequency in the context of photon emission and absorption.
- Which of the following transitions results in the emission of ultraviolet light in hydrogen?
A) n=3 to n=2
B) n=2 to n=1
C) n=4 to n=3
D) n=5 to n=4
Answer: B) n=2 to n=1.
Explanation: The transition from n=2 to n=1 emits ultraviolet light, while other transitions may emit visible or infrared light.
- According to Bohr’s model, the energy of an electron in a hydrogen atom can be expressed as:
A) E = -13.6/n² eV
B) E = 13.6/n² eV
C) E = -n²/13.6 eV
D) E = n²/13.6 eV
Answer: A) E = -13.6/n² eV.
Explanation: The energy levels of the electron in a hydrogen atom are quantized, and the formula shows that energy becomes less negative as n increases.
- Which of the following best describes the condition for an electron to occupy an orbit according to the Bohr model?
A) It must have infinite energy.
B) Its angular momentum must be an integer multiple of h/2π.
C) It must always be in motion.
D) It must be located at the nucleus.
Answer: B) Its angular momentum must be an integer multiple of h/2π.
Explanation: This quantization condition is fundamental to the Bohr model, determining the allowed orbits for electrons.
- The Balmer series corresponds to transitions to which energy level?
A) n=1
B) n=2
C) n=3
D) n=4
Answer: B) n=2.
Explanation: The Balmer series involves electron transitions to the second energy level, resulting in visible light emissions.
- Which of the following statements about electron orbits in the Bohr model is incorrect?
A) Orbits are circular.
B) Electrons can exist between orbits.
C) Orbits have quantized energy levels.
D) Angular momentum is quantized.
Answer: B) Electrons can exist between orbits.
Explanation: According to the Bohr model, electrons cannot exist between defined orbits; they can only occupy specific energy levels.
- In the context of the Bohr model, what is meant by “ionization energy”?
A) Energy required to move an electron to a higher level.
B) Energy required to remove an electron from an atom.
C) Energy released when an electron falls to the ground state.
D) Energy absorbed during excitation.
Answer: B) Energy required to remove an electron from an atom.
Explanation: Ionization energy is the energy needed to completely remove an electron from an atom, typically from the ground state.
- Which of the following statements is true about the transition from n=2 to n=1 in hydrogen?
A) It absorbs energy.
B) It emits infrared light.
C) It emits ultraviolet light.
D) It results in ionization.
Answer: C) It emits ultraviolet light.
Explanation: This transition releases energy in the ultraviolet range, characteristic of the Lyman series.
- The spectral lines in hydrogen are a result of what process?
A) Nuclear reactions
B) Electron transitions
C) Chemical bonding
D) Thermal excitation
Answer: B) Electron transitions.
Explanation: The distinct spectral lines in hydrogen arise from electrons transitioning between different energy levels.
- What does the term “ground state” refer to in the Bohr model?
A) Highest energy level of an electron.
B) Lowest energy level of an electron.
C) Any excited state of an electron.
D) Ionized state of an atom.
Answer: B) Lowest energy level of an electron.
Explanation: The ground state is the most stable and lowest energy configuration of an electron in an atom.
Leave a comment