Ncert Solutions For Class 9 Science Chapter 4 Structure of the Atom

Download NCERT Solutions for Class 9 Science

Chapter 4 Structure of The Atom

(Link of Pdf File is given below at the end of the Questions List)

In this pdf file you can see answers of following Questions

NCERT Solutions of Intext Questions Page 47

Question 1. What are canal rays?

Question 2. If an atom contains one electron and one proton, will it carry any charge or not?

NCERT Solutions of Intext Questions Page 49

Question 1. On the basis of Thomson’s model of an atom, explain how the atom is neutral as a whole.

Question 2. On the basis of Rutherford’s model of an atom, which subatomic particle is present in the nucleus of an atom?

Question 3. Draw a sketch of Bohr’s model of an atom with three shells.

Question 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?

NCERT Solutions of Intext Questions Page 50

Question 1. Write the distribution of electrons in carbon and sodium atoms.

Question 2. If K and L shells of an atom are full, then what would be the total number of electrons in the atom?

NCERT Solutions of Intext Questions Page 52

Question 1. How will you find the valency of chlorine, sulphur and magnesium?

NCERT Solutions of Intext Questions Page 53

Question 1. For the symbol H,D and T tabulate three sub-atomic particles found in each of them.

Question 2. Write the electronic configuration of any one pair of isotopes and isobars.

NCERT Solutions Exercise Questions

Question 1. Compare the properties of electrons, protons and neutrons.

Question 2. What are the limitations of J.J. Thomson’s model of the atom?

Question 3. What are the limitations of Rutherford’s model of the atom?

Question 4. Describe Bohr’s model of the atom.

Question 5. Compare all the proposed models of an atom given in this chapter.

Question 6. Summarise the rules for writing of distribution of electrons in various shells for the first eighteen elements.

Question 7. Define valency by taking examples of silicon and oxygen.

Question 8. Explain with examples
(i) Atomic number
(ii) Mass number
(iii) Isotopes
(iv) Isobars. Give any two uses of isotopes.

Question 9. Na+ has completely filled K and L shells. Explain.

Question 10. If bromine atom is available in the form of, say, two isotopes 79 35 Br (49.7%) and 81 35 Br (50.3%), calculate the average atomic mass of bromine atom.

Question 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?

Question 12. If Z = 3, what would be the valency of the element? Also, name the element.

Question 13. Composition of the nuclei of two atomic species X and Y are given as under X Y Protons = 6 6 Neutrons = 6 8 Give the mass numbers of X and Y. What is the relation between the two species?

Question 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 2000 times that of proton.
(d) An isotope of iodine is used for making tincture iodine, which is used as a medicine. Put tick () against correct choice and cross (×) against wrong choice in questions 15, 16 and 17

Question 15. Rutherford’s alpha-particle scattering experiment was responsible for the discovery of
(a) Atomic Nucleus
(b) Electron
(c) Proton
(d) Neutron

Question 16. Isotopes of an element have
(a) the same physical properties
(b) different chemical properties
(c) different number of neutrons
(d) different atomic numbers.

Question 17. Number of valence electrons in Cl– ion are:
(a) 16
(b) 8
(c) 17
(d) 18

Question 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.

Question 19. Complete the following table.

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