Chapter 4: Structure of the Atom
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Questions and Answers

Which scientist is credited with the discovery of the atomic nucleus?

  • Ernest Rutherford (correct)
  • J.J. Thomson
  • E. Goldstein
  • Neils Bohr

    • What is the relationship between the mass of an electron and the mass of a hydrogen atom?

  • The mass of an electron is about 1 times 2000 the mass of a hydrogen atom. (correct)
  • The mass of an electron is about the same as the mass of a hydrogen atom.
  • The mass of an electron is about 2000 times the mass of a hydrogen atom.
  • The mass of an electron is about 1/2000 the mass of a hydrogen atom.

    • What is the charge of a neutron?

  • Varies depending on the atom
  • Positively charged
  • No charge (correct)
  • Negatively charged

    • Which model of the atom proposed that electrons are distributed in different shells with discrete energy around the nucleus?

    <p>Bohr's model</p> Signup and view all the answers

    What are atoms of different elements with the same mass number called?

    <p>Isobars</p> Signup and view all the answers

    What are canal rays?

    <p>Streams of positively charged particles produced in a discharge tube</p> Signup and view all the answers

    If an atom contains one electron and one proton, will it carry a net charge?

    <p>No, it will be electrically neutral</p> Signup and view all the answers

    According to Thomson's model of an atom, the positive charge is distributed in the form of:

    <p>A diffuse, positively charged sphere</p> Signup and view all the answers

    Which of the following analogies best represents Thomson's model of an atom?

    <p>A plum pudding with raisins distributed throughout</p> Signup and view all the answers

    Which scientist's discovery led to the failure of Dalton's atomic theory?

    <p>Thomson's discovery of electrons</p> Signup and view all the answers

    According to Bohr's model of the atom, why are atoms quite stable?

    <p>Electrons do not radiate energy while revolving in discrete orbits</p> Signup and view all the answers

    What subatomic particle was discovered in the nucleus of an atom according to Rutherford's model?

    <p>Protons</p> Signup and view all the answers

    According to Thomson's model, how is the atom as a whole neutral?

    <p>The positive and negative charges are distributed uniformly throughout the atom</p> Signup and view all the answers

    If the $\alpha$-particle scattering experiment is carried out using a foil of a metal other than gold, what observation would you expect?

    <p>The $\alpha$-particles would be scattered at larger angles</p> Signup and view all the answers

    What was the major contribution of Neils Bohr to the understanding of atomic structure?

    <p>He proposed the existence of discrete energy levels for electrons in an atom</p> Signup and view all the answers

    Which of the following experiments provided evidence that atoms are divisible and have smaller constituents?

    <p>Thomson's cathode ray experiment</p> Signup and view all the answers

    What is the overall charge of an atom in its neutral state?

    <p>Zero</p> Signup and view all the answers

    Which of the following statements about canal rays is correct?

    <p>Canal rays are streams of positively charged particles</p> Signup and view all the answers

    Which subatomic particle was discovered by J.J. Thomson through his cathode ray experiment?

    <p>Electron</p> Signup and view all the answers

    According to the Thomson model of the atom, what is the distribution of positive and negative charges within the atom?

    <p>Negative charges are concentrated in the center, with positive charges surrounding it</p> Signup and view all the answers

    What did Rutherford conclude about the space inside an atom based on the alpha-particle scattering experiment?

    <p>Most of the space inside the atom is empty because most alpha particles passed through the gold foil without deflection.</p> Signup and view all the answers

    Why did Rutherford conclude that the nucleus of an atom is very small?

    <p>Since the size of the nucleus is 105 times less than the radius of the atom.</p> Signup and view all the answers

    What was one of the main drawbacks of Rutherford's model of the atom?

    <p>It failed to describe how electrons lose energy and fall into the nucleus.</p> Signup and view all the answers

    According to Rutherford's nuclear model, where does nearly all of the mass of an atom reside?

    <p>In the positively charged centre called the nucleus.</p> Signup and view all the answers

    Why did Rutherford suggest that charged particles would radiate energy if they revolved in circular orbits?

    <p>Because any particle in a circular orbit would accelerate.</p> Signup and view all the answers

    What is the name of the subatomic particle discovered by Chadwick that has no charge and a mass nearly equal to that of a proton?

    <p>Neutron</p> Signup and view all the answers

    In the helium atom, which has an atomic mass of 4 u and two protons in its nucleus, how many neutrons are present?

    <p>1</p> Signup and view all the answers

    According to the formula for the maximum number of electrons in a shell (2n^2), what is the maximum number of electrons that can be accommodated in the N-shell (n=4)?

    <p>32</p> Signup and view all the answers

    Which of the following statements is true regarding the distribution of electrons in different orbits or shells of an atom?

    <p>The distribution of electrons in different shells was proposed by Bohr and Bury.</p> Signup and view all the answers

    In the representation of a neutron as 'n', what does the symbol 'n' signify?

    <p>The charge of the neutron</p> Signup and view all the answers

    According to Thomson's model of the atom, what is the arrangement of electrons within the atom?

    <p>Electrons are embedded in a positively charged sphere.</p> Signup and view all the answers

    What was the primary observation from Rutherford's alpha particle scattering experiment that contradicted Thomson's model?

    <p>Some alpha particles were deflected at large angles, indicating a dense, positive center in the atom.</p> Signup and view all the answers

    If an atom is electrically neutral, what can be inferred about the relationship between the positive and negative charges within the atom?

    <p>The positive and negative charges are equal in magnitude.</p> Signup and view all the answers

    What was the primary reason for Rutherford's choice of using a gold foil in his alpha particle scattering experiment?

    <p>Gold is a malleable material, allowing for the creation of an extremely thin foil.</p> Signup and view all the answers

    What property of alpha particles made them suitable for Rutherford's scattering experiment?

    <p>Alpha particles are doubly-charged helium ions with a high mass.</p> Signup and view all the answers

    Which of the following statements accurately describes the canal rays observed by Goldstein in his experiments?

    <p>Canal rays are positively charged particles that travel in the opposite direction of cathode rays.</p> Signup and view all the answers

    What is the primary difference between Thomson's and Rutherford's models of the atom?

    <p>Thomson's model assumed electrons were embedded in the atom, while Rutherford's model proposed electrons orbiting the nucleus.</p> Signup and view all the answers

    In Rutherford's alpha particle scattering experiment, what was the expected behavior of the alpha particles based on Thomson's model?

    <p>Alpha particles would experience small deflections due to interactions with the embedded electrons.</p> Signup and view all the answers

    Which of the following statements accurately describes the charge distribution within an atom according to Rutherford's model?

    <p>The positive charge is concentrated in a dense, central nucleus.</p> Signup and view all the answers

    What was the primary reason for selecting a gold foil that was approximately 1000 atoms thick in Rutherford's experiment?

    <p>To ensure that the alpha particles would interact with a sufficient number of atoms.</p> Signup and view all the answers

    What is the valency of magnesium and aluminium?

    <p>2 and 3</p> Signup and view all the answers

    What is the valency of oxygen calculated based on electron distribution?

    <p>2</p> Signup and view all the answers

    How is the maximum number of electrons in the N-shell (n=4) calculated?

    <p>32</p> Signup and view all the answers

    How is valency determined for elements with nearly full outer shells like fluorine?

    <p>By subtracting the number of electrons from the octet.</p> Signup and view all the answers

    What is the significance of the combining capacity of an element, known as valency?

    <p>It determines the number of electrons gained, lost or shared for a full outer shell.</p> Signup and view all the answers

    Explain the distribution of electrons in a carbon atom.

    <p>2, 4</p> Signup and view all the answers

    Describe the distribution of electrons in a sodium atom.

    <p>2, 8, 1</p> Signup and view all the answers

    If the K and L shells of an atom are full, what is the total number of electrons in the atom?

    <p>18</p> Signup and view all the answers

    What is the maximum number of electrons that can be accommodated in the outermost shell of an atom according to the Bohr-Bury model?

    <p>8</p> Signup and view all the answers

    Explain why atoms with 8 electrons in their outermost shell show little chemical activity.

    <p>Zero valency</p> Signup and view all the answers

    Explain the concept of valency in atoms, and how it is related to the number of electrons in the outermost shell.

    <p>Valency is the combining capacity of atoms, determined by the number of electrons in the outermost shell. Atoms tend to react to achieve a fully-filled outermost shell, typically with 8 electrons.</p> Signup and view all the answers

    Describe the electron distribution in the N-shell (n=4) as per the electron distribution table given for the first 18 elements.

    <p>The N-shell can accommodate a maximum of 32 electrons. The electron distribution in the N-shell for the first 18 elements ranges from 0 to 18 electrons.</p> Signup and view all the answers

    What is the electronic configuration of Phosphorus (P) based on the electron distribution table provided?

    <p>The electronic configuration of Phosphorus is 2,8,5. It has 2 electrons in the K-shell, 8 in the L-shell, and 5 in the M-shell.</p> Signup and view all the answers

    Explain the significance of achieving an octet in the outermost shell of an atom.

    <p>Achieving an octet in the outermost shell makes an atom stable and less reactive. It involves atoms gaining, losing, or sharing electrons to reach 8 electrons in the outermost shell.</p> Signup and view all the answers

    Discuss the key differences between Bohr's atomic model and the earlier atomic models proposed by Thomson and Rutherford.

    <p>Bohr's model introduced discrete energy levels and orbits for electrons, unlike the continuous distribution in previous models. It also explained atomic stability with quantized energy levels.</p> Signup and view all the answers

    What is the valency of an element with Z=3? Name the element.

    <p>Valency is 1. Element is Lithium.</p> Signup and view all the answers

    In an atom, what is the maximum number of electrons that can be accommodated in the N-shell (n=4)?

    <p>32 electrons</p> Signup and view all the answers

    What is the correct electronic configuration of sodium?

    <p>2,8,1</p> Signup and view all the answers

    In Rutherford's alpha-particle scattering experiment, what was responsible for the discovery of the Atomic Nucleus?

    <p>Atomic Nucleus</p> Signup and view all the answers

    How many valence electrons does a Cl- ion have?

    <p>8</p> Signup and view all the answers

    Explain the maximum number of electrons that can be accommodated in the M shell of an atom.

    <p>18 electrons</p> Signup and view all the answers

    Define valency and provide the valency of silicon and oxygen.

    <p>Valency is the combining capacity of an atom. Silicon has a valency of 4, while oxygen has a valency of 2.</p> Signup and view all the answers

    Describe Bohr's model of the atom and explain why it was considered an improvement over previous models.

    <p>Bohr's model proposed that electrons move in fixed orbits around the nucleus and explained the stability of atoms. It was an improvement because it successfully explained the line spectra of elements.</p> Signup and view all the answers

    Summarize the rules for writing the distribution of electrons in the first eighteen elements' shells.

    <p>The distribution follows the pattern 2-8-8, starting with the K shell and then filling the L and M shells with electrons.</p> Signup and view all the answers

    Explain with examples the concept of isotopes and calculate the average atomic mass of a bromine atom given two isotopes.

    <p>Isotopes are atoms of the same element with different mass numbers. The average atomic mass of bromine is 79.9 u.</p> Signup and view all the answers

    Explain the concept of isobars in terms of atomic structure.

    <p>Isobars are atoms of different elements with different atomic numbers but the same mass number.</p> Signup and view all the answers

    Describe the electronic configuration of isotopes and isobars.

    <p>Isotopes have the same number of protons but different number of neutrons, leading to different atomic masses. Isobars have the same mass number but different atomic numbers.</p> Signup and view all the answers

    What is the significance of having complete atomic shells according to Bohr's atomic model?

    <p>Complete atomic shells lead to stability and less reactivity of the atom.</p> Signup and view all the answers

    How do electrons, protons, and neutrons contribute to the structure of an atom?

    <p>Electrons are negatively charged and orbit the nucleus; protons are positively charged and reside in the nucleus; neutrons have no charge and are also in the nucleus.</p> Signup and view all the answers

    Explain the concept of sub-atomic particles found in hydrogen isotopes.

    <p>Hydrogen isotopes consist of electrons, protons, and neutrons.</p> Signup and view all the answers

    Explain how to find the valency of chlorine, sulphur, and magnesium.

    <p>Chlorine has a valency of -1, sulphur has a valency of -2, and magnesium has a valency of +2.</p> Signup and view all the answers

    If the number of electrons in an atom is 8 and the number of protons is also 8, what is the atomic number of the atom and what is the charge on the atom?

    <p>The atomic number is 8 and the atom is neutral (charge of 0).</p> Signup and view all the answers

    Using Table 4.1, find the mass number of oxygen and sulphur atoms.

    <p>The mass number of oxygen is 16 and the mass number of sulphur is 32.</p> Signup and view all the answers

    What are isotopes and how do they differ from regular atoms?

    <p>Isotopes are atoms of the same element with the same atomic number but different mass numbers. They differ in the number of neutrons in the nucleus.</p> Signup and view all the answers

    Explain the concept of atomic number and how it is determined in an atom.

    <p>Atomic number is the number of protons in the nucleus of an atom. It is determined by the number of protons an atom possesses.</p> Signup and view all the answers

    What is the significance of the atomic number in defining elements?

    <p>The atomic number determines the identity of an element. All atoms of the same element have the same atomic number.</p> Signup and view all the answers

    Explain how the symbol of an element is written in atomic notation.

    <p>The symbol includes the atomic number (Z), mass number (A), and symbol of the element (e.g., C for carbon).</p> Signup and view all the answers

    Describe the distribution of positive and negative charges within an atom according to Bohr's model.

    <p>In Bohr's model, positive charges are concentrated in the nucleus, while negative charges (electrons) orbit around the nucleus in discrete energy levels.</p> Signup and view all the answers

    What is the maximum number of electrons that can be accommodated in the N-shell (n=4) according to the formula for electron distribution in shells?

    <p>The maximum number of electrons in the N-shell (n=4) is 32.</p> Signup and view all the answers

    Explain why atoms are quite stable according to Bohr's atomic model.

    <p>Atoms are stable in Bohr's model because electrons occupy fixed energy levels and do not emit radiation while orbiting the nucleus.</p> Signup and view all the answers

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