Q1. What subatomic particle carries a positive electrical charge?
a) Neutron
b) Electron
c) Proton
d) Photon
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Correct Answer: c) Proton
Explanation: Protons are subatomic particles found within the nucleus of an atom. They have a positive electrical charge, with a magnitude equal to the negative charge of an electron but opposite in sign. Protons contribute to the mass of an atom, as they have a mass approximately 1,836 times that of an electron. The number of protons in an atom determines its atomic number, which defines the element’s identity. In a neutral atom, the number of protons equals the number of electrons, balancing the positive and negative charges.
Q2. What is the term for the central part of an atom that contains protons and neutrons?
a) Electron cloud
b) Nucleus
c) Electron shell
d) Energy level
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Correct Answer: b) Nucleus
Explanation: The nucleus is the central part of an atom, where protons and neutrons are located. It has a positive electrical charge due to the presence of protons and accounts for almost all of the atom’s mass. The nucleus is surrounded by a region called the electron cloud, where electrons are likely to be found. Despite its small size relative to the overall size of the atom, the nucleus plays a crucial role in determining the atom’s properties and behavior.
Q3. What subatomic particle has a negligible mass and a negative electrical charge?
a) Proton
b) Neutron
c) Electron
d) Photon
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Correct Answer: c) Electron
Explanation: Electrons are subatomic particles that orbit the nucleus of an atom in electron shells or energy levels. They have a negligible mass compared to protons and neutrons, with a mass approximately 1/1836 that of a proton. Electrons carry a negative electrical charge, with a magnitude equal to the positive charge of a proton but opposite in sign. The behavior and arrangement of electrons within an atom determine its chemical properties and reactivity.
Q4. Which of the following statements about neutrons is true?
a) Neutrons have a positive electrical charge.
b) Neutrons are located outside the nucleus of an atom.
c) Neutrons contribute to the mass of an atom but not its charge.
d) Neutrons have a smaller mass than protons.
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Correct Answer: c) Neutrons contribute to the mass of an atom but not its charge.
Explanation: Neutrons are subatomic particles found within the nucleus of an atom. They have a mass approximately equal to that of protons but do not carry an electrical charge (they are electrically neutral). Neutrons play a crucial role in stabilizing the nucleus of an atom through the strong nuclear force, which helps counteract the electrostatic repulsion between positively charged protons. While neutrons contribute to the mass of an atom, they do not affect its overall charge, as they are neutral.
Q5. What term describes the total number of protons and neutrons in the nucleus of an atom?
a) Atomic number
b) Atomic mass
c) Atomic radius
d) Atomic weight
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Correct Answer: b) Atomic mass
Explanation: Atomic mass, also known as atomic mass number or nucleon number, represents the total number of protons and neutrons in the nucleus of an atom. It is typically expressed in atomic mass units (amu) and provides an indication of the atom’s mass relative to a standard reference, such as carbon-12. While the atomic number specifies the number of protons in an atom (which determines its identity), the atomic mass accounts for both protons and neutrons, reflecting the atom’s mass.
Q6. According to the Bohr model, in which orbit or energy level do electrons have the lowest energy?
a) First orbit
b) Second orbit
c) Third orbit
d) Fourth orbit
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Correct Answer: a) First orbit
Explanation: According to the Bohr model of the atom, electrons occupy specific orbits or energy levels around the nucleus. These orbits are numbered starting from the innermost orbit, with the first orbit closest to the nucleus. In the Bohr model, electrons in the first orbit have the lowest energy compared to electrons in higher orbits. The energy of an electron is quantized, meaning it can only exist in specific energy levels, and it transitions between orbits by absorbing or emitting energy in discrete amounts.
Q7. 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: a) Proton < Electron < Neutron
Explanation: In terms of size, protons and neutrons are both located within the nucleus of an atom and have similar sizes, which are much larger than that of electrons. Therefore, the correct order of increasing size for the listed subatomic particles is proton < electron < neutron. While protons and neutrons are comparable in size, electrons are significantly smaller and are located outside the nucleus in electron shells or energy levels.
Q8. 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 finding an electron at various distances from the nucleus, as described by quantum mechanics. The electron cloud is characterized by different shapes and densities, representing different electron orbitals or energy levels. Understanding the electron cloud helps visualize the behavior and arrangement of electrons within an atom.
Q9. 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. Electrons play a crucial role in determining the behavior of elements and their participation in various chemical reactions and processes.
Q10. 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. When an atom gains electrons, it becomes negatively charged (anion), and when it loses electrons, it becomes positively charged (cation). Ions play essential roles in chemical reactions, electrolysis, and the behavior of substances in solution. The formation of ions affects the overall charge and chemical properties of atoms, leading to the creation of charged species with distinct characteristics.