Atomic And Molecular Structure

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  • 1/20 Questions

    Atoms of the same element which have the same number of protons but a different number of neutrons are known as

    • Ions.
    • Isotopes.
    • Neutral atoms.
    • A chemical family.
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Chemistry Quizzes & Trivia
About This Quiz

Multiple choice quiz on atomic and molecular structure and ions.

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  • 2. 

    Mass number refers to:

    • The number of protons in the nucleus of an atom.

    • The number of electrons in an atom.

    • The number of neutrons in an atom.

    • The total number of protons and neutrons in the nucleus of an atom.

    Correct Answer
    A. The total number of protons and neutrons in the nucleus of an atom.
    Explanation
    Mass number refers to the total number of protons and neutrons in the nucleus of an atom. This is because the mass number is a measure of the total mass of an atom, and both protons and neutrons contribute to the mass of an atom. The number of electrons in an atom does not contribute significantly to its mass, as electrons have a much smaller mass compared to protons and neutrons. Therefore, the correct answer is the total number of protons and neutrons in the nucleus of an atom.

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  • 3. 

    An element, X, has the following electron configuration:    2,  5The atomic number of element X would be:

    • 2

    • 5

    • 7

    • 3

    Correct Answer
    A. 7
    Explanation
    The electron configuration of an element indicates the distribution of electrons in its energy levels. In this case, the electron configuration of element X is 2, 5, which means it has 2 electrons in the first energy level and 5 electrons in the second energy level. The atomic number of an element represents the number of protons in its nucleus, which is also equal to the number of electrons in its neutral state. Therefore, since element X has a total of 7 electrons, its atomic number would be 7.

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  • 4. 

    Which of the following statements regarding atomic particles is false?

    • Protons are found in the nucleus and are positively charged particles

    • Electrons move around the nucleus and contribute little to the mass of the atom

    • Neutrons are found in the nucleus and they have no charge

    • The numbers of neutrons, protons and electrons are always equal in a neutral atom

    Correct Answer
    A. The numbers of neutrons, protons and electrons are always equal in a neutral atom
    Explanation
    The statement that the numbers of neutrons, protons, and electrons are always equal in a neutral atom is false. Neutrons and protons are found in the nucleus and have almost the same mass, while electrons are found in the electron cloud surrounding the nucleus and have a much smaller mass. The number of protons determines the element and its atomic number, while the number of neutrons can vary, resulting in different isotopes of the same element. The number of electrons determines the atom's charge, and in a neutral atom, it is equal to the number of protons.

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  • 5. 

    The number of valence electrons in the Group 2 elements of the Periodic Table is

    • 2

    • 4

    • 6

    • 8

    Correct Answer
    A. 2
    Explanation
    The Group 2 elements in the Periodic Table are known as the alkaline earth metals. These elements include beryllium, magnesium, calcium, strontium, barium, and radium. The number 2 is the correct answer because these elements have two valence electrons. Valence electrons are the electrons in the outermost energy level of an atom, and in the case of Group 2 elements, they are found in the s orbital. Having two valence electrons allows these elements to readily lose these electrons and form positive ions with a charge of +2.

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  • 6. 

    Which one of the following is the most important factor that determines the chemical properties of an element?

    • The number of protons in the nucleus of the atom.

    • The total number of electrons in the atom.

    • The number of valence electrons in the atom.

    • The number of neutrons in the nucleus of the atom.

    Correct Answer
    A. The number of valence electrons in the atom.
    Explanation
    The number of valence electrons in an atom is the most important factor that determines the chemical properties of an element. Valence electrons are the outermost electrons in an atom's electron cloud and they are involved in chemical bonding and reactions. The number of valence electrons determines an element's ability to form chemical bonds and participate in chemical reactions. Elements with the same number of valence electrons tend to have similar chemical properties. Therefore, the number of valence electrons is a crucial factor in understanding an element's chemical behavior.

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  • 7. 

    Which of the following is the most important factor in determining the chemical properties of an element?

    • The total number of electrons in its atoms.

    • The number of protons in the nucleus of its atoms.

    • The number of neutrons in the nucleus of its atoms.

    • The number of valence electrons in its atoms.

    Correct Answer
    A. The number of valence electrons in its atoms.
    Explanation
    The chemical properties of an element are primarily determined by the number of valence electrons in its atoms. Valence electrons are the outermost electrons in an atom's electron cloud and are involved in the formation of chemical bonds. These electrons determine the element's reactivity and ability to form compounds with other elements. The total number of electrons in an atom, the number of protons in the nucleus, and the number of neutrons in the nucleus do not directly influence the element's chemical properties as much as the number of valence electrons.

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  • 8. 

    If an element has the electron configuration:  2,  8,  2  then it would most likely form an ion of charge

    • +2

    • -2

    • +6

    • -6

    Correct Answer
    A. +2
    Explanation
    The electron configuration of 2, 8, 2 indicates that the element has 2 electrons in its outermost energy level. In order to achieve a stable electron configuration, it is most likely that this element will lose its 2 outermost electrons to form a positive ion with a charge of +2. This is because elements tend to lose or gain electrons in order to achieve a full outer shell, and in this case, losing 2 electrons would result in a stable configuration similar to that of a noble gas.

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  • 9. 

    The number of valence electrons in an atom is equal to

    • The number of electrons in the atom.

    • The charge on a positive or negative ion formed by that atom.

    • The number of electrons in the outer energy level of the atom.

    • The number of electrons needed to fill all the energy levels of the atom.

    Correct Answer
    A. The number of electrons in the outer energy level of the atom.
    Explanation
    The number of valence electrons in an atom is equal to the number of electrons in the outer energy level of the atom. Valence electrons are the electrons in the outermost energy level of an atom and they are responsible for the atom's chemical properties and reactivity. The other options are incorrect because they do not accurately describe the concept of valence electrons.

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  • 10. 

    The electron configuration:  2, 8, 4 is that of:

    • Carbon

    • Nitrogen

    • Neon

    • Silicon

    Correct Answer
    A. Silicon
    Explanation
    The electron configuration 2, 8, 4 indicates that there are 2 electrons in the first energy level, 8 electrons in the second energy level, and 4 electrons in the third energy level. This configuration matches that of Silicon, which has an atomic number of 14. Carbon has an electron configuration of 2, 4, Nitrogen has an electron configuration of 2, 5, and Neon has an electron configuration of 2, 8. Therefore, the correct answer is Silicon.

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  • 11. 

    Consider three elements A ,B and C which have atomic numbers less than 20. The atomic number of A and B are x and (x-3) respectively. Element A forms cations with formula A+ and forms a solid substance AC when it reacts with element C.Which one of the following elements could  be A?

    • Li

    • Na

    • Cl

    • O

    Correct Answer
    A. Na
    Explanation
    Element A forms cations with formula A+ and reacts with element C to form the solid substance AC. Since element A forms a cation, it must lose electrons to form a positive charge. Elements in group 1 of the periodic table, such as Li and Na, are known to readily lose one electron to form a cation with a +1 charge. Therefore, either Li or Na could be element A. However, since the atomic number of element B is (x-3), it must have a lower atomic number than element A. The atomic number of Na is higher than Li, so Na is the only element that satisfies both conditions. Therefore, Na could be element A.

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  • 12. 

    An element, X, has the following electron configuration:    2,  5The number of valence electrons in element X is

    • 2

    • 5

    • 7

    • 3

    Correct Answer
    A. 5
    Explanation
    The electron configuration of an element represents the arrangement of electrons in its atomic orbitals. In this case, element X has 2 electrons in the first energy level (represented by the number 2) and 5 electrons in the second energy level (represented by the number 5). Valence electrons are the electrons in the outermost energy level, so in this case, element X has 5 valence electrons.

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  • 13. 

    Which one of the following statements about atomic structure is TRUE?

    • The numbers of protons, neutrons and electrons is always equal in a neutral atom.

    • The numbers of protons and neutrons are always equal in a neutral atom.

    • The numbers of neutrons and electrons are always equal in a neutral atom.

    • The numbers of protons and electrons are always equal in a neutral atom.

    Correct Answer
    A. The numbers of protons and electrons are always equal in a neutral atom.
    Explanation
    In a neutral atom, the number of protons is equal to the number of electrons. This is because protons have a positive charge while electrons have a negative charge. In order for an atom to be neutral, the positive charge of the protons must be balanced by the negative charge of the electrons. Therefore, the number of protons and electrons is always equal in a neutral atom.

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  • 14. 

    Electrons are thought to be located in distinct energy levels or shells in an atom. The maximum number of electrons which can be found in the third (n=3) shell of an atom is:

    • 2

    • 8

    • 18

    • 36

    Correct Answer
    A. 18
    Explanation
    The third shell of an atom, also known as the n=3 shell, can hold a maximum of 18 electrons. This is determined by the formula 2n^2, where n is the number of the shell. In this case, 2(3)^2 = 2(9) = 18. Therefore, the correct answer is 18.

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  • 15. 

    The electron configuration for Al3+ is

    • 2, 8, 3

    • 2, 8

    • 2, 8, 6

    • 2, 8, 2

    Correct Answer
    A. 2, 8
    Explanation
    The electron configuration for Al3+ is 2, 8. This is because aluminum (Al) has an atomic number of 13, which means it has 13 electrons. When it loses three electrons to form Al3+, it only has 10 electrons remaining. The electron configuration of 2, 8 represents the distribution of these remaining electrons in the energy levels.

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  • 16. 

    Which of the following determines the size of an atom?

    • The number of protons in the atom.

    • The number of neutrons in the atom.

    • The size of the nucleus of the atom.

    • The number of electrons in the atom.

    Correct Answer
    A. The number of electrons in the atom.
    Explanation
    The size of an atom is determined by the number of electrons in the atom. Electrons are negatively charged particles that surround the nucleus of an atom in energy levels or shells. The more electrons an atom has, the larger its size because the electrons occupy larger regions of space. The number of protons and neutrons in the nucleus does not directly affect the size of the atom, as they are concentrated in the small, dense nucleus at the center of the atom.

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  • 17. 

    Which of the following species does NOT have a stable electron configuration (i.e. like those of an inert gas)?

    • Cl-

    • K+

    • Al3+

    • Mg+

    Correct Answer
    A. Mg+
    Explanation
    Mg+ does not have a stable electron configuration like that of an inert gas because it has lost one electron, leaving it with an incomplete outer electron shell. In contrast, Cl-, K+, and Al3+ have achieved a stable electron configuration by either gaining or losing electrons to match the electron configuration of an inert gas.

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  • 18. 

    Consider three elements A ,B and C which have atomic numbers less than 20. The atomic number of A and B are x and (x-3) respectively. Element A forms cations with formula A+ and forms a solid substance AC when it reacts with element C.What would be the formula of a compound formed by combining elements A and B?

    • AB

    • A2B

    • AB2

    • A3B

    Correct Answer
    A. A2B
    Explanation
    Element A forms cations with a charge of +1, indicated by the formula A+. Element C reacts with A to form a compound with the formula AC. Since A has a charge of +1, it can combine with C which has a charge of -1. Therefore, the compound AC is formed. Element B has an atomic number of (x-3) and since it is less than 20, it can also form a cation with a charge of +1. Therefore, when elements A and B combine, they will form a compound with the formula A2B, as each A atom will have a charge of +1 and each B atom will also have a charge of +1. Hence, the correct answer is A2B.

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  • 19. 

    Consider three elements A ,B and C which have atomic numbers less than 20. The atomic number of A and B are x and (x-3) respectively. Element A forms cations with formula A+ and forms a solid substance AC when it reacts with element C.The most likely type of bond formed between A and B would be:

    • Metallic bonds

    • Covalent bonds.

    • Ionic bonds.

    • Hydrogen bonds.

    Correct Answer
    A. Ionic bonds.
    Explanation
    Element A forms cations with formula A+ when it reacts with element C, indicating that A loses electrons to form a positive charge. This suggests that A is a metal. Element B, on the other hand, has an atomic number (x-3) which is smaller than x, indicating that B is also a metal. When two metals react, they typically form ionic bonds. Ionic bonds involve the transfer of electrons from one atom to another, resulting in the formation of positively charged cations and negatively charged anions. Therefore, the most likely type of bond formed between A and B would be ionic bonds.

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  • 20. 

    Consider three elements A ,B and C which have atomic numbers less than 20. The atomic number of A and B are x and (x-3) respectively. Element A forms cations with formula A+ and forms a solid substance AC when it reacts with element C.Which one of the following elements could be B?

    • Li

    • Na

    • Cl

    • O

    Correct Answer
    A. O
    Explanation
    Element A forms cations with formula A+, which means it loses one electron to form a positive ion. Element C reacts with A to form a solid substance AC. Therefore, element C must have one more electron than element A. Element B has an atomic number of (x-3), which means it has three less electrons than element A. Among the given options, only oxygen (O) has three more electrons than both Li and Na. Therefore, element B could be O.

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  • Current Version
  • Mar 21, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Feb 21, 2010
    Quiz Created by
    Brown.phil

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