- When a hydrogen atom’s electron is in the ground state, it is in which energy level?
A) n=0
B) n=1
C) n=2
D) n=3
Answer: B) n=1.
Explanation: The ground state of a hydrogen atom corresponds to the lowest energy level, which is n=1.
- What energy change occurs when an electron moves from n=2 to n=3 in a hydrogen atom?
A) Energy is absorbed.
B) Energy is emitted.
C) No energy change occurs.
D) Energy becomes negative.
Answer: A) Energy is absorbed.
Explanation: Moving to a higher energy level requires the absorption of energy.
- Which of the following is a characteristic feature of the Lyman series in hydrogen?
A) Emission of visible light.
B) Transitions to n=2.
C) Emission of ultraviolet light.
D) Transitions to n=3.
Answer: C) Emission of ultraviolet light.
Explanation: The Lyman series involves transitions to the ground state (n=1) and results in ultraviolet emissions.
- In the context of the Bohr model, what happens to an electron that gains energy?
A) It becomes ionized.
B) It moves to a lower energy level.
C) It transitions to a higher energy level.
D) It remains in the same energy level.
Answer: C) It transitions to a higher energy level.
Explanation: Gaining energy allows the electron to move to an excited state in a higher energy level.
- Which energy level corresponds to the highest energy in a hydrogen atom?
A) n=1
B) n=2
C) n=3
D) n=∞
Answer: D) n=∞.
Explanation: The level at n=∞ indicates that the electron is no longer bound to the atom, representing its highest energy state.
- What is the effect of increasing the nuclear charge on the energy levels of an atom?
A) Energy levels remain unchanged.
B) Energy levels increase in energy.
C) Energy levels decrease in energy.
D) Energy levels become undefined.
Answer: B) Energy levels increase in energy.
Explanation: Increasing the nuclear charge pulls electrons closer, raising their energy levels.
- In the hydrogen atom, which transition results in the emission of a photon with the longest wavelength?
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: D) n=5 to n=4.
Explanation: Transitions with smaller energy differences, like n=5 to n=4, emit longer wavelength photons.
- How does the Bohr model explain the spectral lines of hydrogen?
A) Through chemical reactions.
B) By assuming random electron movements.
C) By quantizing electron orbits and transitions.
D) By neglecting energy levels.
Answer: C) By quantizing electron orbits and transitions.
Explanation: The spectral lines result from quantized energy transitions between defined electron orbits.
- Which quantum number indicates the orientation of an orbital?
A) Principal quantum number (n)
B) Azimuthal quantum number (l)
C) Magnetic quantum number (m)
D) Spin quantum number (s)
Answer: C) Magnetic quantum number (m).
Explanation: The magnetic quantum number (m) determines the orientation of the orbital in space.
- Which phenomenon does the Bohr model not accurately predict?
A) Hydrogen atom spectrum.
B) Fine structure of spectral lines.
C) Multi-electron systems.
D) Electron transitions.
Answer: B) Fine structure of spectral lines.
Explanation: The Bohr model does not account for the fine structure caused by spin-orbit coupling in more complex atoms.
- In the context of the Bohr model, what is the significance of the electron’s velocity in its orbit?
A) It is constant regardless of energy level.
B) It decreases as the radius increases.
C) It increases as the radius increases.
D) It is irrelevant to electron energy.
Answer: B) It decreases as the radius increases.
Explanation: As electrons move to higher orbits with larger radii, their velocity decreases due to the reduced attractive force from the nucleus.
- Which of the following correctly represents the energy levels of an electron in a hydrogen-like atom?
A) E = -Z²/n² eV
B) E = Z/n² eV
C) E = -n²/Z eV
D) E = Z²/n eV
Answer: A) E = -Z²/n² eV.
Explanation: In hydrogen-like atoms, energy levels are defined by the atomic number (Z), modifying the energy levels compared to hydrogen.
- When electrons fall to the n=3 energy level in hydrogen, they are part of which series?
A) Lyman series
B) Balmer series
C) Paschen series
D) Brackett series
Answer: C) Paschen series.
Explanation: The Paschen series consists of transitions that fall to the n=3 level and are in the infrared range.
- Which type of light is associated with the electron transitions from n=1 to n=2 in the hydrogen atom?
A) Infrared light
B) Ultraviolet light
C) Visible light
D) X-rays
Answer: B) Ultraviolet light.
Explanation: This transition emits ultraviolet light, part of the Lyman series spectrum.
- According to the Bohr model, the maximum number of electrons in a shell is given by what formula?
A) 2n
B) 2n²
C) n²
D) n
Answer: B) 2n².
Explanation: The maximum number of electrons in a shell is calculated by the formula 2n², where n is the principal quantum number.
- What occurs during a “spin flip” of an electron in an atom?
A) Change in energy level
B) Change in angular momentum
C) Change in spin state
D) Change in mass
Answer: C) Change in spin state.
Explanation: A spin flip refers to the electron’s change in spin orientation, affecting its magnetic properties.
- In the Bohr model, which of the following statements is true regarding electron orbits?
A) Electrons can occupy any orbit.
B) Electrons in lower orbits have higher energy.
C) Electrons can only exist in certain fixed orbits.
D) Electrons are always in motion around the nucleus.
Answer: C) Electrons can only exist in certain fixed orbits.
Explanation: The Bohr model postulates that electrons exist in quantized orbits around the nucleus, where they can only occupy specific energy levels.
- What does the azimuthal quantum number (l) determine?
A) The size of the orbital.
B) The shape of the orbital.
C) The orientation of the orbital.
D) The energy of the orbital.
Answer: B) The shape of the orbital.
Explanation: The azimuthal quantum number (l) defines the shape of the electron’s orbital, with different values corresponding to different shapes (s, p, d, f).
- Which of the following is an implication of the Heisenberg uncertainty principle?
A) The position and momentum of an electron can be precisely known simultaneously.
B) The energy levels of electrons are fixed and defined.
C) There is a fundamental limit to the precision with which certain pairs of properties can be known.
D) Electrons travel in circular orbits around the nucleus.
Answer: C) There is a fundamental limit to the precision with which certain pairs of properties can be known.
Explanation: The Heisenberg uncertainty principle states that the more accurately one property (like position) is known, the less accurately the other (like momentum) can be known.
- In the context of the hydrogen atom, which series corresponds to transitions from higher energy levels to n=2?
A) Lyman series
B) Balmer series
C) Paschen series
D) Brackett series
Answer: B) Balmer series.
Explanation: The Balmer series consists of transitions that end at the n=2 level and result in visible light emissions.
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