Atoms and Molecules class 9 MCQs and Answers with FREE PDF

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1. The present concept of the structure of an atom is given by which scientist?
a) Rutherford
b) Goldstein
c) Niels Bohr
d) J.J. Thomson

2. Which model does not able to explain the stability of an atom?

a) Bohr’s Model
b) Rutherford’s Model
c) Thomson’s Model
d) None of the above

3. Who had discovered electron?
a) Niels Bohr
b) E. Goldstein
c) J.J.Thomson
c) James Chadwick

4. The correct electronic configuration of sodium is:a) 2,8,1
b) 8,2,1
c) 2,1,8
d) 2,8,2

5. What is an electron?
a) A wave
b) A particle
c) Either of two, depending on how it is observed
d) Neither of these

6. The cathode ray experiment was done for the first time by:
a) J.J. Thomson
b) John Dalton
c) Goldstein
d) Rutherford

7. The nucleus of an atom contains:
a) Protons
b) Electrons
c) Protons and neutrons
d) Neutrons

8.Which of the following statements is incorrect for cathode rays?
a) They move in straight line
b) Their nature depends upon the nature of gas present in the discharge tube.
c) They cost shadow of solid objects placed in their path
d) They get deflected towards positive charge.

9. The isotopes of an element have:
a) Same number of neutrons
b) Same atomic number
c) Same mass number
d) None of these

10. Which of the following statements is not correct for Bohr’s model of an atom?
a) The nucleus of an atom is situated at ts centre
b) The electrons move in circular orbits
c) Electrons jumps from one orbit to another
d) An electron neither loses nor gains energy it jumps from one orbit to another.

11. Which of the following have equal number of neutrons and protons?
a) Hydrogen
b) Deuterium
c) Fluorine
d) Chlorine

12. The number of electrons in an element with atomic number X and atomic mass Y will be:
a) (X – Y)
b) (Y – X)
c) (X + Y)
d) X

13. The relative atomic masses of many elements are not whole numbers because:
a) They cannot be determined accurately
b) The atoms ionize during determination of their masses
c) Existence of isotopes
d) Presence of impurities

14. Which of the following has a charge of +1 and a mass of 1 amu?
a) A neutron
b) A proton
c) An electron
d) A helium nucleus

15. Which of the following isotopes is used as the standard for atomic mass?
a) 12C
b) 16O
c) 13C
d) 1H

16. Which f the following is not a basic particle of an element?
a) An atom
b) A molecule
c) An ion
d) None

17. Which of the following pairs are isotopes?
a) Oxygen and ozone
b) Ice and steam
c) Nitric oxide and nitrogen dioxide
d) Hydrogen and deuterium

18. Members of which of the following have similar chemical properties?
a) Isotope
b) Isobars
c) Allotropes
d) Both isotopes and allotropes

19. A natural phenomenon that supports the experimental conclusion that atoms are divisible is:
a) Allotropy
b) Radioactivity
c) Cracking
d) None of these

20. Which one of the following statement is not true?
a) Most of the space in an atom is empty
b) The total number of neutrons and protons is always equal in a neutral atom
c) The total number of electrons and protons in an atom is always equal
d) The total number f electrons in any energy level can be calculated by the formula 2n2

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