{"id":8630,"date":"2023-05-29T20:45:25","date_gmt":"2023-05-29T15:15:25","guid":{"rendered":"https:\/\/apboardsolutions.in\/?p=8630"},"modified":"2023-05-30T17:45:38","modified_gmt":"2023-05-30T12:15:38","slug":"ap-board-9th-class-physical-science-important-questions-chapter-5","status":"publish","type":"post","link":"https:\/\/apboardsolutions.in\/ap-board-9th-class-physical-science-important-questions-chapter-5\/","title":{"rendered":"AP Board 9th Class Physical Science Important Questions Chapter 5 What is inside the Atom?"},"content":{"rendered":"

AP State Syllabus AP Board 9th Class Physical Science Important Questions<\/a> Chapter 5 What is inside the Atom?<\/p>\n

AP State Syllabus 9th Class Physical Science Important Questions 5th Lesson What is inside the Atom?<\/h2>\n

9th Class Physical Science 5th Lesson What is inside the Atom? 1 Mark Important Questions and Answers<\/h3>\n

Question 1.
\nWrite any two limitations of Rutherford’s atomic model.
\nAnswer:<\/p>\n

    \n
  • The revolving electron would lose energy continuously and get directed towards positively charged nucleus and eventually crash into the nucleus.<\/li>\n
  • If this is true, the atoms would become highly unstable and the matter would not exist, but matter exists.<\/li>\n<\/ul>\n

    Question 2.
    \nIn Rutherford’s experiment, when the alpha particles hit the foil, Rutherford expected that all the alpha particles would be deflected by small angles. Why did Rutherford expect the above observation?
    \nAnswer:
    \nRutherford thought that positive charge is distributed throughout the atom.<\/p>\n

    \"AP<\/p>\n

    Question 3.
    \nWrite an application of isotopes in the field of medicine.
    \nAnswer:<\/p>\n

      \n
    • The isotope of iodine is used in the treatment of goitre.<\/li>\n
    • The istope of cobalt is used in the treatment of cancer.<\/li>\n<\/ul>\n

      9th Class Physical Science 5th Lesson What is inside the Atom? 2 Marks Important Questions and Answers<\/h3>\n

      Question 1.
      \nWhat is valency? Write valency of hydrogen.
      \nAnswer:<\/p>\n

        \n
      • The number of electrons present in outer most orbit of an atom is called its valency.<\/li>\n
      • Valency of hydrogen is 1.<\/li>\n<\/ul>\n

        Question 2.
        \nObserve the table given below.<\/p>\n\n\n\n\n\n\n\n
        Shell<\/td>\nShell No<\/td>\nMaximum number of electrons in a shell<\/td>\n<\/tr>\n
        K<\/td>\n1<\/td>\n2(1)2<\/sup> = 2<\/td>\n<\/tr>\n
        L<\/td>\n2<\/td>\n2(2)2<\/sup> = 8<\/td>\n<\/tr>\n
        M<\/td>\n3<\/td>\n2 (3)2<\/sup> = 18<\/td>\n<\/tr>\n
        N<\/td>\n4<\/td>\n2(4)2<\/sup> = 32<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        Answer the following questions.
        \ni) Which Shell has highest number of electrons?
        \nii) Write the general form of the formula to find maximum number of electrons in each shell?
        \nAnswer:
        \ni) 0 Shell ‘N’.
        \nii) 2n2<\/sup> (n = 1, 2, 3, ……..)<\/p>\n

        \"AP<\/p>\n

        Question 3.
        \nConvert 36g of water into mole?
        \nAnswer:
        \nWater molecular formula = H2<\/sub>O
        \nAt.wt. of water = (2 \u00d7 1) + 16 = 18
        \n1 mole, water = 18 gr.
        \n36g. of water = \\(\\frac{36}{18}\\) = 2 moles<\/p>\n

        9th Class Physical Science 5th Lesson What is inside the Atom? 4 Marks Important Questions and Answers<\/h3>\n

        Question 1.
        \nFill the blanks in the table using the given information. (Isotopes are not included).
        \n\"AP
        \nAnswer:
        \n\"AP<\/p>\n

        Question 2.
        \nFill in the missing information in the table given below.
        \n\"AP
        \nAnswer:
        \n\"AP<\/p>\n

        Question 3.
        \nDraw the figures showing arrangement of electrons for the given elements.
        \n1. Helium, Oxygen, Argon.
        \nAnswer:
        \n1) Helium
        \n2) Oxygen
        \n3) Argon
        \n\"AP<\/p>\n

        2. How many neutrons are present in the nucleus of Sodium?
        \nAnswer:
        \nSodium = 23<\/sup>11<\/sub>Na
        \nNeutrons = 23-11 = 12<\/p>\n

        Question 4.
        \na) Draw neat diagrams indicating the nucleus and arragement of electrons in different shell for the following elements?
        \ni) Helium
        \nii) Carbon
        \niii) Argon
        \nAnswer:
        \n\"AP<\/p>\n

        b) Which of the above element is unstable? Why?
        \nAnswer:
        \nCarbon is unstable. The nudes of carbon-14 atoms are unstable because they have too many neutrons relative to protons, so they gradually decay.<\/p>\n

        9th Class Physical Science 5th Lesson What is inside the Atom? Important Questions and Answers<\/h3>\n

        9th Class Physical Science 5th Lesson What is inside the Atom? 1 Mark Important Questions and Answers<\/span><\/p>\n

        Question 1.
        \nWrite the names of isotopes of Hydrogen.
        \nAnswer:
        \nHydrogen, deuterium, tritium.<\/p>\n

        Question 2.
        \nWhich element has maximum number of isotopes?
        \nAnswer:
        \nCesium and Helium are the elements having maximum number of isotopes.<\/p>\n

        Question 3.
        \nWhat is maximum number of electrons present in M-shell?
        \nAnswer:
        \nMaximum number of electrons present in M-shell is 2 \u00d7 32 = 2 \u00d7 9 = 18.<\/p>\n

        \"AP<\/p>\n

        Question 4.
        \nWhich atom doesn’t contain neutron in its nuclear?
        \nAnswer:
        \nHydrogen.<\/p>\n

        Question 5.
        \nShow the arrangement of electrons in phosphorus through a diagram.
        \nAnswer:
        \nAtomic number of phosphorus is 15.
        \nDistribution of electrons : 2, 8, 5.
        \n\"AP<\/p>\n

        Question 6.
        \nWho proposed rules for electron distribution in an atom?
        \nAnswer:
        \nBohr and Bury.<\/p>\n

        Question 7.
        \nWhat is the first rule of Bohr and Bury for electron distribution in an atom?
        \nAnswer:
        \nThe maximum number of electrons present in a shell is given by the formula 2n\u00b2, where ‘n’ is the shell number, which takes values 1, 2, 3, 4,<\/p>\n

        Question 8.
        \nWrite the second principle of Bohr – Bury.
        \nAnswer:
        \nEach energy level or electron shell is further divided into sub-shells. The maximum number of electrons that can be accommodated in each shell is 8.<\/p>\n

        \"AP<\/p>\n

        Question 9.
        \nWrite the third law of Bohr – Bury.
        \nAnswer:
        \nElectrons cannot be filled in a given shell unless the inner shells are completely filled i.e., shells are filled in step-wise manner.<\/p>\n

        Question 10.
        \nWhat is an octet?
        \nAnswer:
        \nAn outermost shell which has 8 electrons is said to possess an octet.<\/p>\n

        Question 11.
        \nDefine atomic number.
        \nAnswer:
        \nAtomic number :
        \nAtomic number is the number of protons in the nucleus of an atom, denoted by ‘Z’.<\/p>\n

        Question 12.
        \nDefine atomic mass number.
        \nAnswer:
        \nAtomic mass number:
        \nAtomic mass number is the number of protons plus the number of neutrons, denoted by A.
        \n\u2235 A = Z + N<\/p>\n

        \"AP<\/p>\n

        Question 13.
        \nOn the basis of Thomson’s model of an atom, explain how the atom is neutral as a whole.
        \nAnswer:
        \nThe negative and positive charges are equal in magnitude are present in atom. So, the atom as a whole is electrically neutral as whole according to Thomson model.<\/p>\n

        Question 14.
        \nOn the basis of Rutherford model of an atom, which sub-atomic particle is present in the nuclear of an atom?
        \nAnswer:
        \n\u03b1 – particles are repelled by the nucleus. So it contains positive charged particle that is proton.<\/p>\n

        9th Class Physical Science 5th Lesson What is inside the Atom? 2 Marks Important Questions and Answers<\/span><\/p>\n

        Question 1.
        \nWhat are the postulates of Thomson’s model of the atom?
        \nAnswer:
        \nJ.J. Thomson proposed a model of atom in 1898. The main postulates are
        \n\"AP<\/p>\n

          \n
        1. An atom is considered to be a sphere of uniform positive charge and electrons are embedded into it.<\/li>\n
        2. The total mass of the atom is considered to be uniformly distributed throughout the atom.<\/li>\n
        3. The negative and the positive charges are supposed to cancel out the atom as a whole is electrically neutral.<\/li>\n<\/ol>\n

          This model is commonly known as plum pudding model or watermelon model.<\/p>\n

          Question 2.
          \nWhat are the features of Rutherford’s model of atom?
          \nAnswer:
          \nIn 1909, Rutherford proposed a model of atom based on the alpha particle scattering experiment. The main features are<\/p>\n

            \n
          1. All the positively charged material in an atom formed a small dense centre, called the nucleus of the atom. The electrons were not a part of nucleus.<\/li>\n
          2. The negatively charged electrons revolve around the nucleus in well-defined orbits.<\/li>\n
          3. The size of the nucleus is very small as compared to the size of the atom.<\/li>\n<\/ol>\n

            This model is known as planetary model because the electrons revolve around the nucleus as planets revolve around the sun.<\/p>\n

            This model failed to explain the stability of atom.<\/p>\n

            Question 3.
            \nWrite the rules proposed by Bohr – Bury for electron distribution.
            \nAnswer:
            \nBohr-Bury proposed the following rules for electron distribution.
            \nRule – 1 :
            \nThe maximum number of electrons that can be accommodated in each shell is given by a formula 2n2. Where n is the shell number, which takes the values 1, 2, 3,….
            \nEx : For K shell, n = 1<\/p>\n

            \u2234 Maximum number of electrons in K shell = 2(1)2 = 2 \u00d7 1=2<\/p>\n

            Rule – 2 : Each energy level or electron shell is further divided into subshell. The maximum number of electrons that can be accommodated in each subshell is 8.<\/p>\n

            Rule – 3: Electron cannot be filled in a given shell unless the inner shells are completely filled.<\/p>\n

            \"AP<\/p>\n

            Question 4.
            \nExplain the distribution of electrons in oxygen atom using Bohr-Bury principle.
            \nAnswer:<\/p>\n

              \n
            1. Atomic number of oxygen is 8.<\/li>\n
            2. Hence it has 8 protons and 8 electrons.<\/li>\n<\/ol>\n

              Step -1 :
              \nThe K-shell can accommodate maximum 2 electrons, so the first 2 electrons fill the shell of n = 1.<\/p>\n

              Step – 2 :
              \nThe other 6 electrons will fill the higher shell n = 2 or the L-shell.
              \nStep – 3 :
              \nThen the electronic structure for oxygen atom is 2, 6.<\/p>\n

              Question 5.
              \nFluorine atom contains 7 electrons in the outermost shell. But its valency is ‘1’. Explain.
              \nAnswer:<\/p>\n

                \n
              • Valency is the number of electrons present in the outer most orbit of an atom.<\/li>\n
              • The distribution of electrons in fluorine (atomic number 9) is 2, 7.<\/li>\n
              • Hence the valency of fluorine could be 7.<\/li>\n
              • But it is easier to fluorine to gain one electron for becoming octet.<\/li>\n
              • Hence its valency is determined by subtracting seven electrons from 8 and which gives you a valency ‘1’ for fluorine.<\/li>\n<\/ul>\n

                Question 6.
                \nWhat is the importance of valency?
                \nAnswer:
                \n1) An atom with 8 electrons or an octet in their outer most shell is chemically stable or does not combine other atoms.
                \nEx : Ne, Ar, etc.<\/p>\n

                2) An atom with duplet or 2 electrons in its outer most shell is also more stable when there is only one shell present in it.
                \nEx : He<\/p>\n

                3) Atoms of an element thus react with other atoms. So as to achieve an octet in their shell.<\/p>\n

                4) When elements reacts to form compounds, their atoms must be combining in such a way that they can attain the stable electron distribution of noble gases or inert gases.<\/p>\n

                \"AP<\/p>\n

                Question 7.
                \nHow can an atom achieve octet?
                \nAnswer:
                \nAn atom can achieve an octet by two ways.<\/p>\n

                  \n
                1. One by transfer of electrons.<\/li>\n
                2. Other by sharing of electrons.<\/li>\n
                3. Both the processes results in the formation of bonds between atoms.<\/li>\n<\/ol>\n

                  Question 8.
                  \nExplain the notation : \\({ }_{9}^{19} \\mathrm{F}\\)
                  \nAnswer:<\/p>\n

                    \n
                  • F is the symbol of element (Fluorine).<\/li>\n
                  • 9 is the atomic number.<\/li>\n
                  • 19 is the mass number.<\/li>\n
                  • Hence fluorine has 9 protons and (19 – 9 = 10) 10 neutrons in its nucleus.<\/li>\n
                  • 9 electrons are revolving around the nucleus.<\/li>\n<\/ul>\n

                    Question 9.
                    \nDefine isotope and give two examples.
                    \nAnswer:
                    \nIsotope :
                    \nThe atoms of the same element which have the same number of protons but have different number of neutrons are called isotopes.
                    \n\"AP<\/p>\n

                    Question 10.
                    \n“Sulphur shows multiple valency.” Explain this.
                    \nAnswer:
                    \na) Atomic number of sulphur is 16.
                    \nb) The distribution of electrons is 2, 8, 6.
                    \nc) Hence the valency should be \u20196′.
                    \nd) But it is easier to sulphur to gain 2 electrons than loosing 6 electrons to become octet. Hence its valency would become 2.
                    \ne) So, sulphur shows multiple valency, i.e., ‘2’ or ‘6’.<\/p>\n

                    Question 11.
                    \nShow the arrangement of electrons in first 18 elements schematically.
                    \nAnswer:
                    \n\"AP<\/p>\n

                    Question 12.
                    \nWhat are the applications of isotopes in our daily life?
                    \nAnswer:
                    \nApplications of isotopes :<\/p>\n

                      \n
                    1. Some isotopes are used for solving chemical and medical mysteries.<\/li>\n
                    2. Isotopes are also commonly used in the laboratory to investigate the steps of a chemical reaction.<\/li>\n
                    3. The isotope of uranium is used as a fuel in nuclear reactors.<\/li>\n
                    4. The isotope of iodine is used in the treatment of goitre.<\/li>\n
                    5. The isotope of cobalt is used in the treatment of cancer.<\/li>\n<\/ol>\n

                      Question 13.
                      \nIf an atom contains one electron and one proton, will it carry any charge or not?
                      \nAnswer:
                      \nIt will not carry any charge because proton is positively charged particle and electron is negatively charged particle. So they would neutralise each other.<\/p>\n

                      Question 14.
                      \nWhat do you think would be the observation if the a – particle scattering experiment is carried out using a foil of metal other than gold?
                      \nAnswer:
                      \nGold has highest malleability and ductility. Extremely very thin foil can be prepared by using Gold, which is not possible with other metals. So, we will not get same type of results using other metals.<\/p>\n

                      \"AP<\/p>\n

                      Question 15.
                      \nHelium atom has an atomic mass of 4u and two protons in its nucleus. How many neutrons does it have?
                      \nAnswer:
                      \nAtomic mass due to protons = 2 \u00d7 1 = 2 u
                      \nNeutrons have almost same mass as protons.
                      \nMass of neutrons = 4 – 2 = 2u
                      \n\u2234 Number of neutrons = 2<\/p>\n

                      Question 16.
                      \nWrite the distribution of electrons in carbon and sodium atoms.
                      \nAnswer:
                      \nDistribution of electrons in carbon is 2, 4.
                      \nDistribution of electrons in sodium is 2, 8, 1.<\/p>\n

                      Question 17.
                      \nIf K and L shells of an atom are full, then what would be the total number of electrons in the atom?
                      \nAnswer:
                      \nNumber of electrons present in K shell = 2(1)\u00b2 = 2 \u00d7 1=2
                      \nNumber of electrons present in L shell = 2(2)\u00b2 = 2 \u00d7 4 = 8
                      \nTotal number of electrons in the atom = 2 + 8 = 10<\/p>\n

                      Question 18.
                      \nIf number of electrons in an atom is 8 and number of protons is also 8, then
                      \ni) what is the atomic number of atom?
                      \nii) what is the charge on the atom?
                      \nAnswer:
                      \ni) The atomic number of atom is 8.
                      \nii) The electronic configuration of atom is 2, 6. By gaining two electrons it will get nearest inert gas configuration Neon. So, the charge on the atom is – 2.<\/p>\n

                      \"AP<\/p>\n

                      Question 19.
                      \nChlorine occurs in two isotopic forms that is \\({ }_{17}^{35} \\mathrm{Cl}\\) and \\({ }_{17}^{37} \\mathrm{Cl}\\). The percentage of these forms are 75% and 25% respectively. Find atomic weight of chlorine atom?
                      \nAnswer:
                      \nThe atomic mass of an element is taken as an average mass of all the naturally occurring atoms of the sample element.
                      \nThe average atomic mass of chlorine atom on the bases of above data
                      \n\"AP<\/p>\n

                      Question 20.
                      \nFor the symbol H, D and T tabulate three sub atomic particles found in each of them.
                      \nAnswer:
                      \n\"AP<\/p>\n

                      Question 21.
                      \nNa+<\/sup> has completely filled K and L shells. Explain.
                      \nElectron configuration of Na+ is 2, 8.
                      \nSo, sodium has completed filled K and L shells because the maximum number of electrons filled in K and L shells are 2 and 8 electrons respectively.<\/p>\n

                      Question 22.
                      \nIf Bromine atom is available in the form of say, two isotopes \\({ }_{35}^{79} \\mathrm{Br}\\)(49.7%) and \\({ }_{35}^{81} \\mathrm{Br}\\) (50.3%), calculate the average atomic mass of Bromine atom.
                      \nAnswer:
                      \n\"AP<\/p>\n

                      Question 23.
                      \nThe average atomic mass of sample of an element X is 16.2 u. What are the percentages of isotopes \\({ }_{8}^{16} \\mathrm{X}\\) and \\({ }_{8}^{18} \\mathrm{X}\\)?
                      \nAnswer:
                      \n\"AP
                      \n\u2234 The percentage of first isotope is 90 and percentage of second isotope is 10.<\/p>\n

                      Question 24.
                      \nIf Z = 3, what would be the valency of the elements? Also, name the element?
                      \nAnswer:
                      \nElectronic configuration of element is 2, 1 and the element is Lithium.
                      \nThe element will get nearest inert gas Helium configuration by loosing one electron. So its valency is 1.<\/p>\n

                      Question 25.
                      \nComposition of nuclei of two atomic species X and Y are given as under.<\/p>\n\n\n\n\n\n
                      <\/td>\nX<\/td>\nY<\/td>\n<\/tr>\n
                      Protons<\/td>\n6<\/td>\n6<\/td>\n<\/tr>\n
                      Neutrons<\/td>\n6<\/td>\n8<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

                      Give the mass number of X and Y. What is the relation between the two species?
                      \nAnswer:
                      \nMass number of X = 6 + 6 = 12
                      \nMass number of Y = 6 + 8 = 14
                      \nSo these two species have same atomic number (same number of protons) and different mass numbers. Therefore these two species are isotopes.<\/p>\n

                      9th Class Physical Science 5th Lesson What is inside the Atom? 4 Marks Important Questions and Answers<\/span><\/p>\n

                      Question 1.
                      \nHow did the idea of sub-atomic particles evolve?
                      \nAnswer:<\/p>\n