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 sum of number of protons and number of neutrons present in the nucleus of an atom is called its atomic number mass number all of the above number of electrons None 2. Which of the following is not a correct statement according to Rutherford's atomic model? The size of nucleus is very small in comparison to the atom. Electrons revolve around the nucleus in a fixed circular path. 99% of mass of an atom is centered in the nucleus. Most of the part inside the atom is empty. None 3. 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. (ii) and (iii) only (i) (i) and (iv) (i) and (iii) None 4. The introduction of a neutron into the nuclear composition of an atom would lead to a change in: The chemical nature of the atom Its atomic number The number of the electrons also Its atomic weight None 5. 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 6. How many sub-atomic particles are present in an α- particle used in Rutherford's scattering experiment? Protons - 2, Neutron - 2, Electron - 0 Protons - 4, Neutrons - 0, Electrons - 0 Protons - 2, Neutrons - 0, Electron - 2 Protons - 2, Neutron - 2, Electron - 1 None 7. 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. Goldstein Electrons by J. Chadwick and nucleus by E. Rutherford Electrons by E. Rutherford and nucleus by J.J. Thomson Electrons by J.J. Thomson and nucleus by E. Rutherford None 8. The ratio of the radii of the first three Bohr orbits is: 1:8:27 1:5:33 1:4:9 1:2:3 None 9. If an electron moves away from nucleus, its potential energy: not changes none of these increases decreases None 10. The radius of the first Bohr orbit of hydrogen atom is r. The radius of the 3 rd orbit would be: 3r None of these 27r 9r None 11. Goldsteins experiments which involved passing high voltage electricity through gases at very low pressure resulted in the discovery of: Electron Neutron Nucleus Proton None 12. Which one of the following is considered as the main postulate of Bohr's model of atom Centrifugal force produced due to the revolving electrons balances the force of attraction between electron and protons Angular momentum of electron is an integral multiple of h/2π Electrons are revolving around the nucleus Protons are present in the nucleus None 13. The nucleus of helium contains Four protons Four neutrons Four protons and two electrons Two neutrons and two protons None 14. Bohr's theory can be applied to determine the? first ionization energy of Be atom Electronegativity of Li 2+ ion second ionization energy of helium atom electron gain enthalpy of hydrogen atom None 15. The expression for Bohr's radius of an atom is $$r=\frac{n^{2}h^{2}}{4\pi^{2}me^{4}z^{2}}$$ $$r=\frac{n^{2}h^{2}}{4\pi^{2}m^{2}e^{2}z^{2}}$$ $$r=\frac{n^{2}h^{2}}{4\pi^{2}me^{2}z}$$ $$r=\frac{n^{2}h^{2}}{4\pi^{2}me^{2}z^{2}}$$ 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.
