Q11. What is the term for the average mass of an atom of an element, taking into account the abundance of its isotopes?
a) Atomic mass
b) Atomic weight
c) Atomic number
d) Atomic radius
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Correct Answer: b) Atomic weight
Explanation: Atomic weight is the average mass of an atom of an element, taking into account the relative abundance of its isotopes in nature. It is often listed on the periodic table below the element’s symbol and is expressed in atomic mass units (amu).
Q12. According to the Aufbau principle, in which order do electrons fill the energy levels or electron shells of an atom?
a) From highest to lowest energy levels
b) From lowest to highest energy levels
c) Randomly
d) Based on their mass
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Correct Answer: b) From lowest to highest energy levels
Explanation: The Aufbau principle states that electrons fill the energy levels or electron shells of an atom in order of increasing energy, from the lowest energy level to the highest. This principle helps to determine the electron configuration of atoms and their stability.
Q13. What is the term for the region surrounding the nucleus of an atom where electrons are likely to be found?
a) Nucleus
b) Energy level
c) Electron cloud
d) Electron shell
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Correct Answer: c) Electron cloud
Explanation: The electron cloud is the region surrounding the nucleus of an atom where electrons are likely to be found. It represents the probability distribution of electrons in an atom, as described by quantum mechanics. The electron cloud is characterized by various shapes and densities, representing different electron orbitals.
Q14. Which of the following statements about neutrons in an atom is true?
a) Neutrons have a positive charge
b) Neutrons are located in the nucleus
c) Neutrons orbit the nucleus in specific energy levels
d) Neutrons have a mass approximately equal to that of electrons
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Correct Answer: b) Neutrons are located in the nucleus
Explanation: Neutrons are subatomic particles that have no electrical charge, and they are found in the nucleus of an atom alongside protons. Together, protons and neutrons constitute the majority of an atom’s mass. Neutrons play a crucial role in stabilizing the nucleus through the strong nuclear force, which binds them together with protons. Unlike electrons, which orbit the nucleus in specific energy levels, neutrons are confined within the nucleus.
Q15. What is the term for a shorthand notation used to represent the number of protons, neutrons, and electrons in an atom?
a) Atomic notation
b) Electron configuration
c) Isotopic symbol
d) Lewis symbol
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Correct Answer: c) Isotopic symbol
Explanation: An isotopic symbol is a shorthand notation used to represent the number of protons, neutrons, and electrons in an atom of a specific element or isotope. It typically includes the element’s symbol, atomic number, and mass number. Isotopic symbols provide concise information about the composition of atoms and are commonly used in chemistry and physics.
Q16. According to the Pauli exclusion principle, what is the maximum number of electrons that can occupy an atomic orbital?
a) 1
b) 2
c) 4
d) 8
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Correct Answer: b) 2
Explanation: The Pauli exclusion principle states that no two electrons in an atom can have the same set of quantum numbers. As a result, a maximum of two electrons can occupy an atomic orbital, with opposite spins (up and down). This principle helps to explain the electron configuration of atoms and the behavior of electrons in atoms.
Q17. Which of the following subatomic particles contributes most to the mass of an atom?
a) Proton
b) Neutron
c) Electron
d) Positron
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Correct Answer: b) Neutron
Explanation: Neutrons contribute most to the mass of an atom. Although protons and neutrons have roughly the same mass, electrons have a significantly smaller mass compared to nucleons. Since electrons orbit the nucleus at a relatively large distance, their contribution to the overall mass of an atom is negligible compared to the combined mass of protons and neutrons in the nucleus.
Q18. What is the term for the energy required to remove an electron from an atom in its ground state?
a) Ionization energy
b) Electron affinity
c) Electronegativity
d) Atomic radius
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Correct Answer: a) Ionization energy
Explanation: Ionization energy is the energy required to remove an electron from an atom in its ground state, resulting in the formation of a positively charged ion (cation). Ionization energy is an important property of atoms, as it reflects their tendency to lose electrons and form ions. Elements with low ionization energies tend to be more reactive, as they readily lose electrons to achieve a stable electron configuration.
Q19. Which of the following represents the correct order of increasing size for the listed subatomic particles?
a) Proton < Electron < Neutron
b) Electron < Neutron < Proton
c) Neutron < Electron < Proton
d) Neutron < Proton < Electron
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Correct Answer: c) Neutron < Electron < Proton
Explanation: Neutrons are slightly larger than protons, and both nucleons are significantly larger than electrons. Therefore, the correct order of increasing size for the listed subatomic particles is neutron < electron < proton. The size of an electron is often considered negligible compared to the size of a proton or neutron, which are both located in the nucleus of an atom.
Q20. Which of the following statements about atomic nuclei is true?
a) Atomic nuclei contain only protons and electrons
b) Atomic nuclei are positively charged due to the presence of neutrons
c) Atomic nuclei are held together primarily by the electromagnetic force
d) Atomic nuclei of most elements are stable and do not decay
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Correct Answer: c) Atomic nuclei are held together primarily by the electromagnetic force
Explanation: Atomic nuclei are primarily held together by the strong nuclear force, one of the four fundamental forces of nature. This force overcomes the repulsive electromagnetic force between positively charged protons in the nucleus and binds protons and neutrons together. While the electromagnetic force plays a role in stabilizing nuclei, it is the strong nuclear force that is primarily responsible for nuclear stability.