CBSE Class 9 Science Structure of Atom MCQs Set A

1. The electronic configuration of the element with atomic number 19 is
(A) 2,8,7
(B) 2,9,8
(C) 2,8,8,1
(D) 2,10,7
2. The valence electrons of an element are reponsible for
(A) Physical properties of an element
(B) Chemical properties of an element
(C) Both the properties
(D) None of these
3. An element has electronic configuration 2,8,4 it will be classified as
(A) Metal
(B) Non metal
(C) Metalloid
(D) None of these
4. Isotopes of an element do not have
(A) Same number of element
(B) Same physical properties
(C) Same chemical properties
(D) Same elecrical charge on the nucleus
5. Amongst element X (2,8,6) and (2,8,8) which is more reactive and why ?
(A) X because it is a metal
(B) Y because it is non metal
(C) X because it has 6 valence electrons
(D) Y because it is gas
6. Cathode rays have
(A) Mass only
(B) Charge only
(C) Both mass and charge
(D) Neither mass nor charge
7. Which of these is a pairs isobar ?
(A) 6C12, 8O16 (B) 6C13, 6C14 (C) 20Ca40, 18Ar40 (D) None of these
8. 7N15 and 8O16 are a pair of
(A) Isotopes (B) Isobars (C) Isotones (D) None of these
9. The nucleus of the hydrogen atom is called as
(A) Neutron (B) Electron (C) Proton (D) Nucleons
10. The e/m value for cathode rays
(A) varies with the nature of the gas
(B) does not vary with the nature of gas
(C) could not be determinde by J.J. Thomson
(D) Both (B) & (C) are correct
11. Cathode raysget deflected in a electric field towards
(A) Positive plate
(B) Negative Plate
(C) No deflection takes place
(D) First towards negative plate and then towards positive plate
12. Isotopes differ in
(A) No. of electrons
(B) No. of protons
(C) No. of neutrons
(D) Chemical reactivity
13. The atomic number of an element ‘y’ is 20. The electronic configuration of the ion having inert gas configuration is
(A) 2,8,10 (B) 2,18 (C) 2,10,8 (D) 2,8,8
14. Which amonght the following statement is true?
(A) a rays are cathode rays
(B) Electrons make up the cathode rays
(C) Protons make up the cathode rays
(D) Electron magnetic radiation make up the cathode rays
15. The isotope of hydrogen that contains the same numer of protons and neutrons in its nucleus is called
(A) Protium (B) Deutrium (C) Tritium (D) None of these
16. a particle is emitted by 92X238 during redioactivity. The new specie y should be :
(A) 90Y234 (B) 90Y238 (C) 92Y234 (D) 94Y234
17. When an a-particle is emitted
(A) Element moves 2 places to the right in the periodic table
(B) Element moves one place to the left
(C) Element moves 2 places to the left in the periodic table
(D) Elements maintains its position
18. If the nuclide of actinium 89Ac228, emits b particle, the daughter nuclide will be
(A) 88Ra228 (B) 90Th228 (C) 87Fr224 (D) 90Th229
19. The relative atomic masses of many elements are not whole numbers because
(A) They can’t be determined very accurately
(B) The atoms ionize during the determination
(C) of the existence of isotopes
(D) of the presence of impurities
Answers Key

1 C
2 B
3 C
4 B
5 C
6 C
7 C
8 C
9 C
10 B
11 A
12 C
13 D
14 B
15 B
16 A
17 C
18 B
19 C



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