Ncert – class 9- science – Chapter 4 – Structure of the Atom 2 Welcome to your Ncert - class 9- science - Chapter 4 – Structure of the Atom 2 1. The presence of electrons outside the nucleus and nucleus at the centre of the atom was suggested by: Electrons by J.J. Thomson and nucleus by E. Rutherford Electrons by J.J. Thomson and nucleus by E. Goldstein Electrons by E. Rutherford and nucleus by J.J. Thomson Electrons by J. Chadwick and nucleus by E. Rutherford None 2. Goldsteins experiments which involved passing high voltage electricity through gases at very low pressure resulted in the discovery of: Nucleus Proton Electron Neutron None 3. Which one of the following is considered as the main postulate of Bohr's model of atom Electrons are revolving around the nucleus Protons are present in the nucleus Angular momentum of electron is an integral multiple of h/2π Centrifugal force produced due to the revolving electrons balances the force of attraction between electron and protons None 4. Which of the following statements about Rutherford’s model of atom are correct?(i) Proposed that nearly all the mass of an atom resides in the nucleus.(ii) Established that the �α–particles are four times as heavy as a hydrogen atom.(iii) Considered the nucleus as positively charged.(iv) Agreed with Thomson’s model. (i) and (iii) only (i) (i) and (iv) (ii) and (iii) None 5. How many sub-atomic particles are present in an α- particle used in Rutherford's scattering experiment? Protons - 2, Neutrons - 0, Electron - 2 Protons - 2, Neutron - 2, Electron - 1 Protons - 4, Neutrons - 0, Electrons - 0 Protons - 2, Neutron - 2, Electron - 0 None 6. The nucleus of helium contains Two neutrons and two protons Four protons Four neutrons Four protons and two electrons None 7. The introduction of a neutron into the nuclear composition of an atom would lead to a change in: The number of the electrons also The chemical nature of the atom Its atomic number Its atomic weight None 8. Which of the following is not a correct statement according to Rutherford's atomic model? Electrons revolve around the nucleus in a fixed circular path. Most of the part inside the atom is empty. 99% of mass of an atom is centered in the nucleus. The size of nucleus is very small in comparison to the atom. None 9. The expression for Bohr's radius of an atom is $$r=\frac{n^{2}h^{2}}{4\pi^{2}me^{4}z^{2}}$$ $$r=\frac{n^{2}h^{2}}{4\pi^{2}me^{2}z}$$ $$r=\frac{n^{2}h^{2}}{4\pi^{2}me^{2}z^{2}}$$ $$r=\frac{n^{2}h^{2}}{4\pi^{2}m^{2}e^{2}z^{2}}$$ None 10. If an electron moves away from nucleus, its potential energy: increases none of these decreases not changes None 11. The ratio of the radii of the first three Bohr orbits is: 1:5:33 1:4:9 1:8:27 1:2:3 None 12. Bohr's theory can be applied to determine the? Electronegativity of Li 2+ ion second ionization energy of helium atom first ionization energy of Be atom electron gain enthalpy of hydrogen atom None 13. Neutron is a fundamental particle carrying: No charge and no mass A charge of −1 and a mass of 1 unit No charge and a mass of 1 unit A charge of +1 unit and a mass of unit None 14. The sum of number of protons and number of neutrons present in the nucleus of an atom is called its all of the above atomic number number of electrons mass number None 15. The radius of the first Bohr orbit of hydrogen atom is r. The radius of the 3 rd orbit would be: 3r 27r None of these 9r None Time's up Please Share This Share this content Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Opens in a new window Leave a Reply Cancel replyCommentEnter your name or username to commentEnter your email address to commentEnter your website URL (optional) Save my name, email, and website in this browser for the next time I comment.
