NCERT Science Solutions Class 9th :- Chapter 4 Structure of the Atom Solutions
Structure of the Atom Solutions
In Text Questions
Page No: 47
1. What are canal rays?
2. If an atom contains one electron and one proton, will it carry any charge or not?
Page No: 49
1. On the basis of Thomson’s model of an atom, explain how the atom is neutral as a whole.
2. On the basis of Rutherford’s model of an atom, which subatomic particle is present in the nucleus of an atom?
3. Draw a sketch of Bohr’s model of an atom with three shells.
Bohr’s Model of an atom with three shells
4. What do you think would be the observation if the α-particle scattering experiment is carried out using a foil of a metal other than gold?
1. Name the three sub-atomic particles of an atom.
2. Helium atom has an atomic mass of 4 u and two protons in its nucleus. How many neutrons does it have?
Page No: 50
1. Write the distribution of electrons in carbon and sodium atoms
2. If K and L shells of an atom are full, then what would be the total number of electrons in the atom?
Page No: 52
1. How will you find the valency of chlorine, sulphur and magnesium?
1. If number of electrons in an atom is 8 and number of protons is also 8, then (i) what is the atomic number of the atom and (ii) what is the charge on the atom?
2. With the help of Table 4.1, find out the mass number of oxygen and sulphur atom.
Page No: 53
1. For the symbol H, D and T tabulate three sub-atomic particles found in each of them.
2. Write the electronic configuration of any one pair of isotopes and isobars
Page No: 54
1. Compare the properties of electrons, protons and neutrons.
2. What are the limitations of J.J. Thomson’s model of the atom?
3. What are the limitations of Rutherford’s model of the atom?
4. Describe Bohr’s model of the atom.
5. Compare all the proposed models of an atom given in this chapter.
6. Summarize the rules for writing of distribution of electrons in various shells for the first eighteen elements.
7. Define valency by taking examples of silicon and oxygen.
Page No: 55
8. Explain with examples (i) Atomic number, (ii) Mass number, (iii) Isotopes and (iv) Isobars. Give any two uses of isotopes.
9. Na+ has completely filled K and L shells. Explain.
11. The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes 16 / 8 X and 18 / 8 X in the sample?
12. If Z = 3, what would be the valency of the element? Also, name the element.
13.Composition of the nuclei of two atomic species X and Y are given as under
Protons = 6 6
Neutrons = 6 8
Give the mass numbers of X and Y. What is the relation between the two species?
14. For the following statements, write T for ‘True’ and F for ‘False’.
(a) J.J. Thomson proposed that the nucleus of an atom contains only nucleons.
(b) A neutron is formed by an electron and a proton combining together. Therefore, it is neutral.
(c) The mass of an electron is about 1 / 2000times that of proton.
(d) An isotope of iodine is used for making tincture iodine, which is used as a medicine.
15. Rutherford’s alpha-particle scattering experiment was responsible for the discovery of
(a) Atomic nucleus
16. Isotopes of an element have
(a) the same physical properties
(b) different chemical properties
(c) different number of neutrons
(d) different atomic numbers
17. Number of valence electrons in Cl -ion are:
Page No: 56
18. Which one of the following is a correct electronic configuration of sodium?
(a) 2, 8
(b) 8, 2, 1
(c) 2, 1, 8
(d) 2, 8, 1
19. Complete the following table.