Chapter-4
STRUCTURE OF THE ATOM
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. Summarise 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.
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 shells. Explain.
10. If bromine atom is available in the form of, say, two isotopes 
Br (49.7%) and Br (50.3%), calculate the average atomic mass of bromine atom.
11. The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes 
X and 
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
X Y
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 
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 (x) against wrong choice in questions 15, 16 and 17
15. Rutherford's alpha-particle scattering experiment was responsible for the discovery of
(a) Atomic Nucleus
(b) Electron
(c) Proton
(d) Neutron
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:
(a) 16
(b) 8
(c) 17
(d) 18
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.
Atomic Number | Mass Number | Number Of Neutrons | Number Of Protons | Number Of Electrons | Number Of the Atomic Species |
9 16 - - - | - 32 24 2 1 | 10 - - - 0 | - - 12 1 1 | - - - - 0 | - Sulphur - - - |
Type- Bikash Bora
