structure of atom class 9 important questions
Answers
Answer:
1. Which of the following is the correct electronic configuration for magnesium?
(a) 2, 8, 1
(b) 2, 8, 3
(c) 2, 8, 4
(d) 2, 8, 2
► (d) 2, 8, 2
2. A student weighs 30 kg. Suppose his body is entirely made up of electrons. How many electrons are there in his body?
(a) 3.29 x 1031
(b) 3.29 x 1023
(c) 3.29 x 1030
(d) 3.29 x 1032
► (a) 3.29 x 1031
3. Nucleous consist of
(a) Proton and electron
(b) Proton and neutron
(c) Neutron and electron
(d) Only neutron
► (b) Proton and neutron
4. The electron should be filled in the orbital in accordance with the increasing order of their energy. This statement is related with
(a) Affbau principle
(b) Pauli principle
(c) Hund's principle
(d) Plank's rules
► (a) Affbau principle
5. Which one of the following statements is true according to Rutherford’s nuclear model of an atom?
(a) There is a positively charged centre in an atom called the nucleus.
(b) All the mass of an atom resides in the nucleus.
(c) The electrons revolve around the nucleus in well-defined orbits.
(d) All of the above
► (d) All of the above
6. Which of the following is not true for cathode rays?
(a) Cathode rays consist of negatively charged particles.
(b) Cathode rays were discovered by J.J Thomson.
(c) Nature of cathode rays depend upon the nature of the gas in discharge tube.
(d) Cathode rays are produced inside the discharge tube.
► (c) Nature of cathode rays depend upon the nature of the gas in discharge tube.
7. When alpha-particles are sent through a thin metal foil, most of them go straight through the foil because_______.
(a) alpha-particles are positively charged.
(b) alpha-particles are much smaller than electrons.
(c) alpha-particles move with low velocity.
(d) most part of the atom is empty.
► (d) most part of the atom is empty.
8. What are the essential conditions for the production of anode rays?
(a) High voltage and low pressure
(b) High voltage and high pressure
(c) Low voltage and high pressure
(d) Low voltage and low pressure
► (a) High voltage and low pressure
9. The increasing order of the energy levels in an atom is _______ .
(a) K > L > M > N
(b) L > M > N > K
(c) L < M < N < K
(d) K < L < M < N
► (c) L < M < N < K
10. How many valence electrons are present in a potassium atom?
(a) 2
(b) 1
(c) 3
(d) 8
► (b) 1
11. Which of the following elements has the electron configuration 2?
(a) Magnesium
(b) Helium
(c) Sodium
(d) Hydrogen
► (b) Helium
12. An atom which has a mass number of 14 or 8 neutrons is–
(a) Isotope of oxygen
(b) Isobar of oxygen
(c) Isotope of carbon
(d) Isobar of carbon
► (c) Isotope of carbon
13. The maximum number of electrons that can be accommodated in third shell ( n = 3) is:
(a) 2
(b) 8
(c) 18
(d) 10
► (c) 18
14. N shell can have a maximum of _______ electrons.
(a) 32
(b) 2
(c) 18
(d) 8
► (a) 32
15. Each of the stationary orbits are associated with:
(a) A certain amount of velocity.
(b) A certain amount of mass.
(c) A certain amount of energy.
(d) A certain amount of force.
► (c) A certain amount of energy.
16. The canal rays led to the discovery of which subatomic particle?
(a) Beta rays
(b) Protons
(c) Neutrons
(d) Electrons
► (b) Protons
17. The number of valence electron in Na is
(a) 1
(b) 2
(c) 3
(d) 4
► (a) 1
18. An atomic number of an element equals to what present in the nucleus of its atom?
(a) Protons
(b) Electrons
(c) Neutron
(d) None of the above
► (a) Protons
19. Isotopes of an element have:
(a) the same physical properties
(b) different chemical properties
(c) different number of neutrons
(d) different atomic numbers
► (c) different number of neutrons
20. The conclusion of Rutherford’s scattering experiment does not include
(a) Alpha-particles can come within the distance of order of 10-14 m of the nucleus.
(b) The radius of nucleus is less than 10-14 m.
(c) Scattering follows coulomb’s law, i.e., same charges repel each other.
(d) The positively charged particles of atom move with very high velocity.
► (d) The positively charged particles of atom move with very high velocity.
21. The electronic configuration of an atom with atomic number 19 is:
(a) 2, 8, 8, 1
(b) 1, 2, 2, 8
(c) 2, 8, 9
(d) 2, 10, 7
► (a) 2, 8, 8, 1
22. According to J.J Thomson, an atom is a positively charged sphere. Which sub-atomic particles is embedded in it?
(a) Electrons
(b) Canal Rays
(c) Protons
(d) Neutrons
► (a) Electrons
23. If Z = 6, what would be the valency of the element?
(a) 6
(b) 2
(c) 4
(d) 8
► (c) 4
24. The proton has a charge equal in magnitude but opposite in sign to that of:
(a) neutron
(b) deuterons
(c) electron
(d) canal rays
► (c) electron
25. What is a valence shell?
(a) Third shell
(b) First shell
(c) Outermost shell
(d) Second shell
► (c) Outermost shell
26. Which of the following particles was discovered first?
(a) Neutron
(b) Electron
(c) Proton
(d) Meson
► (b) Electron
Explanation: