Atomic Structure Quiz
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Questions and Answers

What distinguishes isobars from one another?

  • Same chemical properties and different physical properties
  • Same atomic number and different mass numbers
  • Same mass number and different atomic numbers (correct)
  • Different atomic masses and same atomic numbers

    • Which of the following pairs represent isobars?

  • Helium and Hydrogen
  • Ca and Ar (correct)
  • Calcium and Chlorine
  • Carbon and Nitrogen

    • How many protons are in an element with an atomic number of 20?

  • 40 protons and 20 neutrons
  • 40 protons and 40 neutrons
  • 20 protons and 20 neutrons (correct)
  • 20 protons and 40 neutrons

    • Which statement accurately describes isotopes?

    <p>Isotopes differ in their atomic mass</p> Signup and view all the answers

    According to Rutherford’s experiment, where is the mass and positive charge of the atom primarily located?

    <p>Concentrated in the nucleus</p> Signup and view all the answers

    What was the primary conclusion of Dalton's atomic theory?

    <p>Atoms are indivisible.</p> Signup and view all the answers

    Who discovered the electron and in what year?

    <p>J.J. Thomson, 1897</p> Signup and view all the answers

    What charge does a proton carry?

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

    Which experiment led to the discovery of the neutron?

    <p>Alpha Particle Bombardment</p> Signup and view all the answers

    What is the relative mass of a neutron in comparison to a proton?

    <p>Equal to a proton</p> Signup and view all the answers

    In Thomson's atomic model, what was primarily demonstrated?

    <p>Atoms contain negatively charged electrons.</p> Signup and view all the answers

    How does the mass of an electron compare to that of a proton?

    <p>Approximately 1/2000 of a proton's mass</p> Signup and view all the answers

    Which statement regarding atomic charge is correct?

    <p>Protons have a positive charge.</p> Signup and view all the answers

    What is the maximum number of electrons that can be accommodated in the M shell?

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

    Which of the following statements about the outermost shell is correct?

    <p>It can hold exactly 8 electrons.</p> Signup and view all the answers

    In the electron distribution of Ca₂₀, how many electrons are in the M shell?

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

    What determines the valency of an atom?

    <p>The number of valence electrons in the outermost shell.</p> Signup and view all the answers

    According to the octet rule, what do atoms strive to achieve?

    <p>A complete outermost shell of up to 8 electrons.</p> Signup and view all the answers

    Which of these elements follows the duplet rule?

    <p>Helium (He)</p> Signup and view all the answers

    Why do atoms combine with each other?

    <p>To complete their outer shell and achieve a noble gas configuration.</p> Signup and view all the answers

    What is the maximum number of electrons that can be held in the N shell?

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

    What is the charge of the nucleus in an atom according to Rutherford's model?

    <p>Positively charged</p> Signup and view all the answers

    What is the primary reason why Rutherford's model was considered unstable?

    <p>Electrons lose energy and fall into the nucleus</p> Signup and view all the answers

    What did Niels Bohr propose about electrons in his model?

    <p>Electrons revolve in stable orbits without losing energy</p> Signup and view all the answers

    How is an energy level designated in Bohr's model?

    <p>Using letters like K, L, M, and N</p> Signup and view all the answers

    What happens when an electron jumps from a higher energy level to a lower energy level?

    <p>Energy is emitted</p> Signup and view all the answers

    Which statement about atomic number is correct?

    <p>It equals the number of protons in a neutral atom</p> Signup and view all the answers

    What was a significant flaw in Rutherford's model regarding the mass of the atom?

    <p>Neglected the role of neutrons</p> Signup and view all the answers

    What is referred to when an electron is in the lowest energy level?

    <p>Ground state</p> Signup and view all the answers

    What does Thomson's model of the atom suggest about the structure of an atom?

    <p>It consists of a positively charged sphere with electrons embedded within it.</p> Signup and view all the answers

    What were the main observations from Rutherford's gold foil experiment?

    <p>Most alpha particles passed through the foil without deflection.</p> Signup and view all the answers

    What conclusion did Rutherford reach regarding the nucleus of an atom?

    <p>It is positively charged and extremely small compared to the atom.</p> Signup and view all the answers

    What is the approximate size of the nucleus relative to the atom, according to Rutherford?

    <p>About 1/10⁵ of the size of the atom.</p> Signup and view all the answers

    Why did Rutherford choose gold foil for his scattering experiment?

    <p>Gold is the most malleable metal, allowing for thin sheets.</p> Signup and view all the answers

    Which statement best characterizes the atomic model proposed by Thomson?

    <p>Atoms consist of a positively charged sphere with negatively charged electrons embedded.</p> Signup and view all the answers

    What is the reason that an atom is considered electrically neutral in Thomson's model?

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

    What was one of the significant implications of the results from Rutherford's experiments?

    <p>The concept of a dense nucleus was introduced.</p> Signup and view all the answers

    What is the electron distribution of a chlorine atom (atomic number 17)?

    <p>2, 8, 7</p> Signup and view all the answers

    How many electrons does the L shell of a chlorine atom contain?

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

    What is the electronic configuration of a sodium ion (Na+)?

    <p>1s² 2s² 2p⁶</p> Signup and view all the answers

    How many electrons will element X gain to achieve a noble gas configuration if it has 7 electrons in its outermost shell?

    <p>1 electron, resulting in a -1 charge</p> Signup and view all the answers

    What is the mass number of an element that contains 15 electrons and 16 neutrons?

    <p>31</p> Signup and view all the answers

    How many neutrons does a helium atom (mass of 4 u) have if it has two protons?

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

    Which statement is true regarding isotopes?

    <p>Isotopes have the same atomic number but different mass numbers.</p> Signup and view all the answers

    What is a practical application of isotopes?

    <p>Uranium isotopes are used as fuel in nuclear reactors.</p> Signup and view all the answers

    Study Notes

    Atomic Structure

    • Atoms are the fundamental building blocks of matter.
    • Dalton's atomic theory proposed that matter is composed of indivisible atoms.
    • Experiments in the late 19th century revealed subatomic particles, challenging Dalton's concept.

    Discovery of Subatomic Particles

    • J.J. Thomson: Discovered electrons using the cathode ray experiment. Cathode rays exhibited properties of particles irrespective of gas or electrode. Proved atoms are divisible and contain subatomic particles.
    • E. Goldstein: Discovered protons using anode rays/canal rays. These rays are positively charged particles.
    • J. Chadwick: Discovered neutrons. These are neutral particles with mass roughly equal to protons.

    Characteristics of Subatomic Particles

    • Electron (e-): Negatively charged, negligible mass compared to protons and neutrons.
    • Proton (p+): Positively charged, mass is ~2000 times that of an electron
    • Neutron (n°): Neutral, mass is almost equal to proton

    Atomic Models

    • Thomson's Model: Described the atom as a positively charged sphere with negatively charged electrons embedded within it (like a plum pudding).

    • Postulates of Thomson's model:

      • An atom consists of a positively charged sphere with electrons embedded within.
      • The negative and positive charges are equal in magnitude, making the atom electrically neutral.

    • Rutherford's Model: Proposed a nucleus, a small, dense, positively charged center containing most of the atom's mass. Electrons orbit the nucleus.

    • Gold Foil Experiment: Rutherford's experiment where alpha particles were aimed at a thin gold foil. Most particles passed through, but some were deflected, leading to the discovery of the nucleus.

    • Rutherford's Model Postulates:

      • Nucleus is at the center of the atom and contains a positive charge.
      • Most of the atomic mass is concentrated in the nucleus.
      • Nucleus of an atom is very dense. The size of the nucleus is very small compared to the size of the atom.

    • Bohr's Model: Electrons orbit the nucleus in specific, stable energy levels, or shells (K, L, M, N...). Electrons absorb energy to move to higher levels and emit energy to fall to lower levels.

    • Bohr's Postulates:

      • Electrons revolve around the nucleus in stable orbits.
      • Each orbit corresponds to a definite energy level.
      • An electron does not radiate energy while it remains in a particular orbit.
      • Energy is emitted or absorbed by an electron only when it jumps from one allowed orbit to another.

    Atomic Number and Mass Number

    • Atomic Number (Z): The number of protons in an atom. It defines the element.
    • Mass Number (A): The sum of protons and neutrons in an atom.

    Electron Configuration

    • Electrons occupy specific energy levels and orbitals.
    • Bohr-Bury Scheme describes the distribution of electrons within shells (K, L, M, N) and subshells within shells.
    • The outermost shell contains valence electrons that participate in bonding.

    Valency

    • The combining capacity of atoms. It is determined by the number of valence electrons.

    Isotopes

    • Atoms of the same element with different numbers of neutrons.
    • Isotopes have the same atomic number but different mass numbers.
    • Isotopes have similar chemical properties but different physical properties.

    Isobars

    • Atoms of different elements with the same mass number but different atomic numbers.
    • Isobars have different chemical and physical properties.

    Fractional Atomic Mass

    • The average mass of an element considering the different isotopes.
    • Calculated by weighting each isotope's contribution based on its abundance.

    Application of Isotopes

    • Certain isotopes have unique applications in fields like nuclear reactors, medicine, etc.

    TOP 5 Questions

    • Answers to key concepts in a multiple choice format are included in the document.

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    Class 9th Structure of the Atom PDF

    Description

    Test your knowledge of atomic structure concepts including isobars, isotopes, atomic theory, and electron configurations. This quiz will help reinforce your understanding of fundamental principles in chemistry and the characteristics of subatomic particles.

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