Q1. What is the charge of a proton?
a) Positive
b) Negative
c) Neutral
d) Variable
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Correct Answer: a) Positive
Explanation: Protons are subatomic particles found in the nucleus of an atom, and they carry a positive electrical charge. This positive charge is equal in magnitude to the negative charge of electrons, but opposite in sign. Along with neutrons, protons contribute to the atomic mass of an atom. The number of protons in the nucleus determines the element’s atomic number, which defines the chemical properties of the element. Protons play a crucial role in the stability and identity of an atom, as they are involved in interactions with other atoms in chemical reactions.
Q2. What is the charge of an electron?
a) Positive
b) Negative
c) Neutral
d) Variable
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Correct Answer: b) Negative
Explanation: Electrons are subatomic particles with a negative electrical charge. They orbit the nucleus of an atom in specific energy levels or electron shells. Electrons play a significant role in chemical bonding and the reactivity of elements, as they can be transferred or shared between atoms. The negative charge of electrons balances the positive charge of protons in an atom, maintaining overall electrical neutrality.
Q3. What is the charge of a neutron?
a) Positive
b) Negative
c) Neutral
d) Variable
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Correct Answer: c) Neutral
Explanation: Neutrons are subatomic particles found in the nucleus of an atom, and they have no electrical charge, making them electrically neutral. Along with protons, neutrons contribute to the atomic mass of an atom. Neutrons play a crucial role in stabilizing the nucleus through the strong nuclear force, which binds them together with protons. Their neutral charge allows them to interact with other particles without being influenced by electromagnetic forces.
Q4. Which subatomic particle determines the identity of an element?
a) Proton
b) Neutron
c) Electron
d) Positron
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Correct Answer: a) Proton
Explanation: The identity of an element is determined by the number of protons in the nucleus of its atoms. This number is known as the element’s atomic number and is represented by the letter “Z” in the periodic table. Each element has a unique number of protons, which defines its chemical properties and distinguishes it from other elements.
Q5. 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.
Q6. What is the atomic number of an element?
a) The total number of protons and neutrons in the nucleus
b) The total number of neutrons in the nucleus
c) The total number of electrons in the electron cloud
d) The number of protons in the nucleus
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Correct Answer: d) The number of protons in the nucleus
Explanation: The atomic number of an element is the number of protons in the nucleus of its atoms. It is represented by the letter “Z” in the periodic table and determines the element’s identity. Elements with different atomic numbers have distinct chemical properties. The atomic number also determines the number of electrons in a neutral atom, as atoms have an equal number of protons and electrons in their ground state.
Q7. What is the mass number of an atom?
a) The total number of protons in the nucleus
b) The total number of neutrons in the nucleus
c) The sum of protons and neutrons in the nucleus
d) The average mass of all isotopes of the element
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Correct Answer: c) The sum of protons and neutrons in the nucleus
Explanation: The mass number of an atom is the sum of the number of protons and neutrons in its nucleus. It is represented by the letter “A” in the symbol notation of an element, where A = Z + N, with Z being the atomic number (number of protons) and N being the number of neutrons. The mass number determines the atomic mass of an atom and varies among different isotopes of the same element.
Q8. Which of the following statements about isotopes is true?
a) Isotopes have the same number of protons but different numbers of neutrons
b) Isotopes have the same number of neutrons but different numbers of protons
c) Isotopes have different numbers of protons and electrons
d) Isotopes have the same number of protons and neutrons
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Correct Answer: a) Isotopes have the same number of protons but different numbers of neutrons
Explanation: Isotopes are atoms of the same element with the same number of protons (and thus the same atomic number) but different numbers of neutrons in their nuclei. Since isotopes of an element have the same number of protons, they have identical chemical properties. However, due to differences in neutron number, isotopes may have different atomic masses and physical properties.
Q9. What is the term for the weighted average mass of all isotopes of an element?
a) Atomic number
b) Mass number
c) Atomic weight
d) Isotopic mass
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Correct Answer: c) Atomic weight
Explanation: Atomic weight, also known as atomic mass or atomic mass number, is the weighted average mass of all isotopes of an element found in nature. It is determined by considering the relative abundance of each isotope and its respective mass. Atomic weight is often listed on the periodic table below the element’s symbol and is expressed in atomic mass units (amu).
Q10. 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.
Q11. What is the term for the total number of protons and neutrons in the nucleus of an atom?
a) Atomic mass
b) Atomic weight
c) Atomic number
d) Atomic radius
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Correct Answer: a) Atomic mass
Explanation: Atomic mass is the total number of protons and neutrons in the nucleus of an atom. It is typically expressed in atomic mass units (amu) and is an important characteristic used to identify isotopes of an element. The atomic mass provides information about the mass of an atom relative to a standard reference, such as carbon-12.
Q12. According to the Bohr model, 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: According to the Bohr model, electrons fill the energy levels or electron shells of an atom in order of increasing energy, from the lowest energy level (closest to the nucleus) to the highest. Each energy level can hold a specific maximum number of electrons, with higher energy levels accommodating more electrons than lower ones. This model helps to explain the stability and electron configuration of atoms.
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. 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.
Q15. 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.
Q16. Which subatomic particle contributes most to the chemical behavior of an atom?
a) Proton
b) Neutron
c) Electron
d) Positron
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Correct Answer: c) Electron
Explanation: Electrons contribute most to the chemical behavior of an atom. As the outermost subatomic particles, electrons are involved in chemical bonding, reactions, and the formation of compounds. The arrangement and number of electrons in the outermost energy level determine an atom’s chemical properties, including its reactivity and ability to form chemical bonds with other atoms.
Q17. What is the term for an atom or group of atoms that has gained or lost one or more electrons, resulting in a net electrical charge?
a) Ion
b) Isotope
c) Element
d) Molecule
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Correct Answer: a) Ion
Explanation: An ion is an atom or group of atoms that has gained or lost one or more electrons, resulting in a net electrical charge. An ion with a positive charge (due to loss of electrons) is called a cation, while an ion with a negative charge (due to gain of electrons) is called an anion. Ions play crucial roles in chemical reactions, electrolysis, and the behavior of substances in solution.
Q18. What is the term for the process by which an atom gains or loses electrons, resulting in the formation of ions?
a) Ionization
b) Electron affinity
c) Electronegativity
d) Electron configuration
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Correct Answer: a) Ionization
Explanation: Ionization is the process by which an atom gains or loses electrons, resulting in the formation of ions. When an atom loses electrons, it becomes positively charged (cation), while gaining electrons leads to a negative charge (anion). Ionization can occur through various mechanisms, such as chemical reactions, exposure to radiation, or interaction with electric fields.
Q19. What is the term for the outermost energy level of an atom?
a) Valence shell
b) Core shell
c) Orbital shell
d) Electron shell
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Correct Answer: a) Valence shell
Explanation: The valence shell is the outermost energy level or electron shell of an atom. It determines the atom’s chemical behavior and reactivity, as it contains the valence electrons involved in chemical bonding and interactions with other atoms. The number of electrons in the valence shell determines an atom’s valency, which indicates its ability to form chemical bonds with other atoms.
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.