{"id":4372,"date":"2020-08-28T10:16:52","date_gmt":"2020-08-28T04:46:52","guid":{"rendered":"https:\/\/kseebsolutions.guru\/?p=4372"},"modified":"2021-07-02T15:04:06","modified_gmt":"2021-07-02T09:34:06","slug":"kseeb-solutions-class-8-science-chapter-3","status":"publish","type":"post","link":"https:\/\/kseebsolutions.guru\/kseeb-solutions-class-8-science-chapter-3\/","title":{"rendered":"KSEEB Solutions for Class 8 Science Chapter 3 Structure of Atom"},"content":{"rendered":"

Karnataka Board Class 8 Science Chapter 3 Structure of Atom<\/h2>\n

KSEEB Class 8 Science Chapter 3 Textual Questions & Answers<\/h3>\n

I. Four alternatives are given to each of the following incomplete statements, question choose the right answer.<\/p>\n

Question 1.
\nThe heaviest fundamental particle is.
\n(a) Proton
\n(b) electron
\n(c) neutron
\n(d) positron
\nAnswer:
\n(c) neutron<\/p>\n

Question 2.
\nIn the scattering experiment the deflection of alpha particle is due to
\n(a) increase in kinetic energy
\n(b) force of repulsion
\n(c) Force of attraction
\n(d) decrease of kinetic energy
\nAnswer:
\n(b) force of repulsion<\/p>\n

Question 3.
\nThe simplest atom that does not contain neutron is.
\n(a) Deuterium
\n(b) tritium
\n(c) hydrogen
\n(d) helium
\nAnswer:
\n(c) hydrogen<\/p>\n

Question 4.
\nThe reason for the existence of isotopes is change in.
\n(a) Atomic number
\n(b) Electron number
\n(c) Neutron number
\n(d) Proton number.
\nAnswer:
\n(d) Proton number.<\/p>\n

II. Fill in the blanks:<\/p>\n

Question 1.
\nThe total number of protons and neutrons in the nucleus of an atom in known as ……….
\nAnswer:
\nAtomic mass<\/p>\n

Question 2.
\nAlmost all the mass of an atom is concentrated in a small region of space called the ………..
\nAnswer:
\nnucleus<\/p>\n

Question 3.
\nThe particle of an atom that has no charge is ………….
\nAnswer:
\nneutrons<\/p>\n

Question 4.
\nThe fundamental particle not present in a normal hydrogen atom is …………..
\nAnswer:
\nneutron<\/p>\n

Question 5.
\nThe atomic mass of an atom is 23 and its atomic number is 11. The atom has ………….. neutrons.
\nAnswer:
\n12<\/p>\n

III. Answer the following:<\/p>\n

Question 1.
\nState the postulates of Dalton\u2019s atomic theory.
\nAnswer:
\nIn 1803 English chemist Dalton put forward his atomic theory. The main postulates of the theory are as follows.<\/p>\n

    \n
  1. Elements are made up of very small indivisible particles called atoms.<\/li>\n
  2. All atoms of a particular element are identical in shape, mass and other properties, but are different from the atom of other elements.<\/li>\n
  3. Atom of one element can not be converted into that of another element.<\/li>\n
  4. Atoms of an element combine in integral ratio with those of other elements to form a compound<\/li>\n
  5. An atom can neither be created nor destroyed.<\/li>\n<\/ol>\n

    Question 2.
    \nDescribe J.J Thomson\u2019s experiment on the discovery of cathode rays.
    \nAnswer:
    \n\"KSEEB<\/p>\n

    J.J Thomson\u2019s and others conducted an experiment with a vacuum pump. Metal electrodes are fitted to the ends of the glass tube, as shown in the figure. He created very low pressure inside the discharge tube and applied high voltage. He observed a greenish glow near the anode of the glass tube.<\/p>\n

    The rays which are emitted from the cathode hit the anode and cause the greenish glow. The streams of rays emitted from the cathode are called cathode rays. Which are made of small particles? He called electrons.<\/p>\n

    Question 3.
    \nList out the different characteristics of anode rays
    \nAnswer:
    \nThe characteristics of anode rays are:<\/p>\n

      \n
    1. They consist of positively charged particles.<\/li>\n
    2. They are deflected by electrical and magnetic fields. The deflection is very little when compared to the deflection of cathode rays because it consists of heavy particles<\/li>\n
    3. The deflection of the anode rays depends on the nature of the rays in the discharge tube. Heavier the gas lowers the depletion.<\/li>\n<\/ol>\n

      Question 4.
      \nDescribe Rutherford\u2019s model of an atom?
      \nAnswer:
      \n\"KSEEB<\/p>\n

      Ruther ford\u2019s atomic model was also called the nuclear atom or planetary model of the atom. The model described the atom as a tiny dense, positively charged core called a nucleus, in which nearly all the mass is concentrated, around which the light negative constituents called electrons, revolve at some distance, much like planets revolving around the sun.<\/p>\n

      Question 5.
      \nDescribe Neil’s Bohr\u2019s atomic model?
      \nAnswer:<\/p>\n

        \n
      1. Electrons revolve around the nucleus only in certain permissible circular orbits, (orbit is some times called a shell. The first<\/li>\n
      2. shell nearest to the nucleus is called \u2018K.\u2019 shell. The subsequent shells as we move away from the nucleus are L, M, N, O respectively).<\/li>\n
      3. Electrons in each shell have been associated with a definite amount of energy. Electrons in higher shell have more energy than those nearer to the nucleus.<\/li>\n
      4. The energy of an electron remains constant so long as it revolves in its own shell. The shells also represent energy levels.<\/li>\n<\/ol>\n

        Question 6.
        \nMention the properties of cathode rays.
        \nAnswer:
        \nThe properties of cathode rays are,<\/p>\n

          \n
        1. cathode rays are negatively charged particles<\/li>\n
        2. cathode rays are a stream of particles which travels in a straight line.<\/li>\n
        3. Cathode rays can affect a photographic plate<\/li>\n<\/ol>\n

          Question 7.
          \nWho proposed the atomic nucleus is positively charged?
          \nAnswer:
          \nRutherford proposed that the atomic nucleus is positively charged.<\/p>\n

          Question 8.
          \nState the conclusions drawn by the Scattering experiment of Rutherford?
          \nAnswer:
          \nPositively charged particles of an atom are held together in the central region of the atom. It is called the nucleus. It is surrounded by electrons.<\/p>\n

            \n
          1. The volume of the nucleus is small when compared to the volume of an atom.<\/li>\n
          2. The mass of an atom is concentrated in the nucleus.<\/li>\n
          3. The nucleus is positively charged which is different in magnitude for different elements.<\/li>\n
          4. In a neutral atom, the number of electrons outside the nucleus are equal to the number of positively charged particles in the nucleus<\/li>\n<\/ol>\n

            Question 9.
            \nWhy is an atom neutral in-spite of the presence of charged particles in it?
            \nAnswer:
            \nThe number of positively charged particles (protons) in the nucleus is equal to the number of negatively charged particles (electrons) outside the nucleus. Therefore an atom is neutral.<\/p>\n

            Question 10.
            \nList the three fundamental particles and their properties.
            \nAnswer:
            \nThe fundamental particles present in an atom are.<\/p>\n

              \n
            1. Positively charged particles called protons (p)<\/li>\n
            2. The negatively charged particles called electrons (e) and.<\/li>\n
            3. neutral particles called neutrons (n)<\/li>\n<\/ol>\n

              Question 11.
              \nDefine the term atomic number and atomic mass number of an element.
              \nAnswer:<\/p>\n

                \n
              1. Atomic number: The number of protons present in the nucleus of an atom is known as the atomic number.
                \nIt is denoted by \u2018Z\u2019<\/li>\n
              2. Atomic mass number: The total number of protons and neutrons present in the nucleus of an atom is known as mass number. It is denoted by A.<\/li>\n<\/ol>\n

                Generally, the atomic number and mass number of the atom of an element is represented by a symbol ZXA.<\/sup>
                \n\u2018X\u2019 is an element.<\/p>\n

                Question 12.
                \nDefine the term Isotope of an atom with a suitable example.
                \nAnswer:
                \nAtoms of an element with different mass numbers are called Isotopes.
                \nEx: Hydrogen has three types of atoms,<\/p>\n

                  \n
                1. 1<\/sub>H1<\/sup> (protium)<\/li>\n
                2. 1<\/sub>H2<\/sup> (deuterium)<\/li>\n
                3. 1<\/sub>H3<\/sup> (tritium)<\/li>\n<\/ol>\n

                  Question 13.
                  \nFrom the symbol 19k40 state
                  \n(1) mass number of potassium
                  \n(2) atomic number of potassium
                  \n(3) write the distribution of electrons in an atom of potassium.
                  \nAnswer:<\/p>\n

                    \n
                  1. The mass number of potassium (A)= 40<\/li>\n
                  2. The atomic number of potassium (Z)=19<\/li>\n
                  3. The electronic configuration of potassium = 1S2<\/sup>, 2S2<\/sup>2Ps<\/sup>\u00a03S2<\/sup>3P6<\/sup>, 4S1<\/sup><\/li>\n<\/ol>\n

                    IV. Match the following:
                    \n\"KSEEB
                    \nAnswer:<\/p>\n

                      \n
                    1. (f)
                      \n<\/span><\/li>\n
                    2. (d)
                      \n<\/span><\/li>\n
                    3. (a)
                      \n<\/span><\/li>\n
                    4. (e)<\/span><\/li>\n<\/ol>\n

                      KSEEB Class 8 Science Chapter 3 Additional Questions & Answers<\/h3>\n

                      Question 1.
                      \nWhat is an element?
                      \nAnswer:
                      \nAny Substance made up of same kind of atom is called an element. 118 elements are known to us.<\/p>\n

                      Question 2.
                      \nWrite an experiment to show that the cathode rays are made up of high-velocity material particles
                      \nAnswer:
                      \n\"KSEEB<\/p>\n

                      J.J Thomson placed a light paddle wheel in the path of cathode rays. The paddle wheel started to rotate this can happen only if the material particles have high velocity.<\/p>\n

                      Question 3.
                      \nWrite an Experiment to demonstrate the properties of cathode rays.
                      \nAnswer:
                      \n\"KSEEB<\/p>\n

                      J.J. Thomson applied an electric field parallel to the path of the rays. The cathode rays deflected towards the anode. He concluded that cathode rays negatively charged.<\/p>\n

                      Question 4.
                      \nList out the characteristics of cathode rays.
                      \nAnswer:
                      \nThe characteristics of cathode rays are:<\/p>\n

                        \n
                      1. They consist of negatively charged particles.<\/li>\n
                      2. cathode rays are also called as electrons.<\/li>\n
                      3. electrons are lighter than the Hydrogen atom.<\/li>\n
                      4. electrons mass is very small or less.<\/li>\n<\/ol>\n

                        Question 5.
                        \nDescribe the gold stein experiment on the discovery of anode rays.
                        \nAnswer:
                        \n\"KSEEB<\/p>\n

                        In 1886 Gold stein used a modified type of discharged tube with a perforated cathode. He observed that certain rays are traveling in the direction opposite to that of cathode rays. He applied an electric field parallel to the path of rays and observed that the path deflected towards the cathode. Since these rays contain positively charged particles he called positive rays or anode rays.<\/p>\n

                        Question 6.
                        \nWhen the hydrogen gas is taken inside the discharge tube the deflection will be maximum give season.
                        \nAnswer:
                        \nThe positive particles of hydrogen atoms are the lightest hence the deflection will be maximum.<\/p>\n

                        Question 7.
                        \nDescribe the alpha-particle scattering experiment conducted by rutherford.
                        \nAnswer:
                        \n\"KSEEB
                        \nRutherford directed high speed positively charged particles called alpha particles towards a thin gold foil. He observed that most of the alpha particles passed through the foil without deflection. A few of them were deflected at very large angles from their original direction and a few were even turned back on their path.<\/p>\n

                        Question 8.
                        \nWhy did most of the alpha particles pass through the foil?
                        \nAnswer:
                        \nMost of the alpha particles passed through the foil because most of the space in the atom was empty.<\/p>\n

                        Question 9.
                        \nWhy did a Few of them alpha particles deflect their original path through large angles?
                        \nAnswer:
                        \nThe deflection was due to the enormous repulsive force.<\/p>\n

                        Question 10.
                        \nState the conclusions drawn by Scattering experiment of rutherford.
                        \nAnswer:<\/p>\n

                          \n
                        1. Positively charged particles of an atom are held together in the central region of the atom. It is\u201d called the nucleus. It is surrounded by electrons.<\/li>\n
                        2. The volume of nucleus is small when compared to the volume of an atom.<\/li>\n
                        3. The mass of an atom is concentrated in the nucleus.<\/li>\n
                        4. The nucleus is positively charged which is different in magnitude for different elements.<\/li>\n
                        5. In a neutral atom the number of electrons outside the nucleus are equal to the number of positively charged particles in the nucleus.<\/li>\n<\/ol>\n

                          Question 11.
                          \nRuther ford atomic model could of explain the stability of the atom. Explain the above statement.
                          \nAnswer:
                          \nAn electron revolving around the nucleus continuously should lose energy. As a result, it should be gradually pulled towards the nucleus and end up colliding with it. if this should happen then the atom would collapse \u2018Rutherford\u2019s atomic model could not explain the stability of the atom.<\/p>\n

                          Question 12.
                          \nState the postulates of the Bohr model.
                          \nAnswer:
                          \nIn 1913 Neil’s Bohr presented a model of an atom which is now called the model. The postulates of this model are.<\/p>\n

                            \n
                          1. Electron revolves around the nucleus only in certain permissible circular orbits called shells.<\/li>\n
                          2. The shells are designated by the letters K.L.M.N. O.P. etc.<\/li>\n
                          3. Electron in each shell has been associated with a definite amount of energy. Electrons in higher shell have more energy than those nearer to the nucleus.<\/li>\n
                          4. The energy of an electron remains constant as long as it revolves in its own shell.<\/li>\n<\/ol>\n

                            Question 13.
                            \nFrom the symbol 17 CI35 <\/sup>state
                            \n(1) mass number chlorine
                            \n(2) atomic number of chlorine
                            \n(3) write the distribution of electron in an atom of chlorine.
                            \nAnswer:<\/p>\n

                              \n
                            1. The mass number of chlorine (A) = 35<\/li>\n
                            2. The atomic number of chlorine (z) = 17
                              \nThe number of electron = number of protons = 17<\/li>\n
                            3. The electronic configuration of chlorine = 1S2<\/sup>, 2S2<\/sup>2P6<\/sup>, 3S2<\/sup>3P5<\/sup><\/li>\n<\/ol>\n

                              Question 14.
                              \nMention the uses of Isotopes?
                              \nAnswer:<\/p>\n

                                \n
                              1. \u00a0Medical Science
                                \na) Treatment of cancer
                                \nb) Treatment of thyroid<\/li>\n
                              2. \u00a0In industries to check defects
                                \na) To check faults in machinery.<\/li>\n<\/ol>\n

                                KSEEB Solutions for Class 8 Science<\/a><\/h4>\n","protected":false},"excerpt":{"rendered":"

                                Karnataka Board Class 8 Science Chapter 3 Structure of Atom KSEEB Class 8 Science Chapter 3 Textual Questions & Answers I. Four alternatives are given to each of the following incomplete statements, question choose the right answer. Question 1. The heaviest fundamental particle is. (a) Proton (b) electron (c) neutron (d) positron Answer: (c) neutron …<\/p>\n","protected":false},"author":5,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6],"tags":[],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/posts\/4372"}],"collection":[{"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/comments?post=4372"}],"version-history":[{"count":0,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/posts\/4372\/revisions"}],"wp:attachment":[{"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/media?parent=4372"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/categories?post=4372"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/kseebsolutions.guru\/wp-json\/wp\/v2\/tags?post=4372"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}