MCQ 21
What is the significance of the wave function (ψ) in quantum mechanics?
A) It determines the exact position of an electron.
B) It describes the probability distribution of an electron.
C) It represents the energy of an electron.
D) It is irrelevant to the behavior of electrons.
Answer: B) It describes the probability distribution of an electron.
Explanation: The wave function (ψ) provides information about the probability of finding an electron in a certain region of space, not its exact position.
MCQ 22
What happens to the energy levels of electrons as you move to higher principal quantum numbers?
A) They decrease.
B) They remain the same.
C) They increase.
D) They become negative.
Answer: C) They increase.
Explanation: As the principal quantum number (n) increases, the energy levels of electrons increase, indicating that the electrons are located farther from the nucleus.
MCQ 23
Which of the following statements about the photon is true?
A) It has mass.
B) It has a charge.
C) It exhibits both wave and particle characteristics.
D) It is always in a stationary state.
Answer: C) It exhibits both wave and particle characteristics.
Explanation: A photon is a quantum of electromagnetic radiation that behaves both as a wave and as a particle, demonstrating wave-particle duality.
MCQ 24
What is the electron configuration of oxygen (atomic number 8)?
A) 1s² 2s² 2p²
B) 1s² 2s² 2p⁴
C) 1s² 2s² 2p⁶
D) 1s² 2s² 2p³
Answer: B) 1s² 2s² 2p⁴.
Explanation: The electron configuration for oxygen, which has 8 electrons, fills the 1s and 2s orbitals first, followed by four electrons in the 2p orbitals.
MCQ 25
What is the term for the energy required to remove an electron from an atom in its gaseous state?
A) Electron affinity
B) Ionization energy
C) Electronegativity
D) Atomic radius
Answer: B) Ionization energy.
Explanation: Ionization energy is the energy required to remove an electron from an isolated atom in the gas phase, and it indicates how strongly an atom holds onto its electrons.
MCQ 26
Which of the following elements has the highest electronegativity?
A) Fluorine
B) Oxygen
C) Nitrogen
D) Carbon
Answer: A) Fluorine.
Explanation: Fluorine is the most electronegative element, meaning it has the highest tendency to attract electrons in a chemical bond.
MCQ 27
Which quantum number is not required for specifying an electron in a hydrogen atom?
A) Principal quantum number (n)
B) Azimuthal quantum number (l)
C) Magnetic quantum number (m_l)
D) Spin quantum number (m_s)
Answer: B) Azimuthal quantum number (l).
Explanation: In hydrogen, the energy levels depend only on the principal quantum number (n), so the azimuthal quantum number (l) does not influence the energy.
MCQ 28
What is the correct order of filling orbitals according to the Aufbau principle?
A) 1s, 2s, 2p, 3s, 3p, 4s, 3d
B) 1s, 2s, 2p, 3s, 3d, 4s
C) 1s, 2s, 3s, 3p, 4s, 3d
D) 1s, 2s, 3s, 3p, 4s, 4p
Answer: A) 1s, 2s, 2p, 3s, 3p, 4s, 3d.
Explanation: The correct filling order follows the Aufbau principle, which prioritizes the lowest energy levels first, including 4s before 3d.
MCQ 29
Which of the following is true about the ground state of an atom?
A) Electrons are in the highest energy state.
B) Electrons fill higher orbitals first.
C) Electrons occupy the lowest available energy levels.
D) All orbitals are half-filled.
Answer: C) Electrons occupy the lowest available energy levels.
Explanation: In the ground state, electrons are arranged in the lowest possible energy levels according to the Aufbau principle, maximizing stability.
MCQ 30
In which of the following configurations does the element exhibit paramagnetism?
A) 1s² 2s² 2p⁶
B) 1s² 2s² 2p⁴
C) 1s² 2s² 2p³
D) 1s² 2s² 2p²
Answer: C) 1s² 2s² 2p³.
Explanation: An element exhibits paramagnetism when it has unpaired electrons. Configuration C has three unpaired electrons in the 2p orbitals, making it paramagnetic.
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