Class 9 science chapter 4 Structure of an Atom mcqs

                                                                                               Class 9 Science

                                                              Chapter – 4 Structure of Atoms

(1) Atomic number (Z) is equal to ————–

(a) Number of protons in the nucleus of an atom.    (b) Number of electrons in a neutral atom

(c) Both (a) and (b)        (d) None of the above

(2) Two atoms are said to be Isobars if ————–

(a) They have same atomic number but different mass number

(b) They have same number of electrons but different number of neutrons

(c) They have the same number of neutrons but different numbers of electrons.

(d) None of the above

(3) Mass of proton is ————

(a) 1.000 amu (b) 0.9073 amu (c) 1.0073 amu (d) 5.486 x 10-4 amu

(4) The mass number of the element is —————

(a) the sum of the number of electrons and protons   (b) the sum of the number of protons and neutrons

(c) the number of neutrons      (d) the number of protons

(5) The atomic number of an element is equal to ————

(a) number of neutrons    (b) number of electrons   (c) number of protons   (d) number of neutrons + number of protons

(6) An alpha particle is also known as ————–

(a) subatomic particle    (b) an unionised helium atom    (c) a neutral particle    (d) a doubly-charged helium ion

(7) Which of the following statements about the electron is incorrect?

(a) It is a negatively charged particles

(b) The mass of the electron is equal to the mass of the neutron

(c) It is a basic constituent of all atom

(d) It is a constituent of cathode rays

(8) How many electrons are occupied in the M shell?

(a) 8   (b) 16    (c) 18    (d) 32

(9) Who discovered the electron?

(a) Goldstein   (b) J.J Thomson   (c) Chadwick    (d) Eugen Goldstein                                                                                

(10)  7N15 and 8O16 are pair of ———-

(a) Isotopes   (b) Isobars   (c) Isotones    (d) none of these

(11) The electronic configuration of the element with atomic number 19 is

(a) 2,8,7   (b) 2,8,8   (c) 2,8,8,1   (d) 2,8,8,2

(12) The valence electrons of an element are responsible for –

(a) Physical properties of an element (b) Chemical properties of an element (c) Both the properties  (d) None of these

(13) An element has an electronic configuration 2,8,4 it will be classified as –

(a) Metal   (b) Non-metal (c) Metalloid   (d) None of these

(14) Isotopes of an element do not have

(a) Same number of element   (b) Same physical properties    (c) Same chemical properties  (d) Same electrical charge on the nucleus

(15) 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

(16) Cathode rays have –

(a) Mass only     (b) Charge only   (c) Both mass and charge only   (d) Neither mass nor charge

(17) Which of these is a pairs isobar ?

(a) 6C12, 8O16    (b) 6C13, 6C14     (c) 20Ca40, 18Ar40   (d) None of these

(18) 7N15 and 8O16 are a pair of –

(a) Isotopes   (b) Isobars   (c) Isotones  (d) None of these

(19) The nucleus of the hydrogen atom is called as-

(a) Neutron   (b) Electron   (c) Proton  (d) Nucleons

(20) Isotopes differ in –

(a) No of electrons  (b) No of protons   (c) No of Neutrons   (d) Chemical reactivity

(21) Which amongst the following statement is true?

(a) rays are cathode rays    (b) Electrons make up the cathode rays   (c) Protons make up the cathode rays   (d) Electrons magnetic radiation make up the cathode rays

(22) The isotope of hydrogen that contains the same number of protons and neutrons in its nucleus is called –

(a) Protium   (b) Deutrium    (c) Tritium  (d) None of these

(23) The shells or orbits are denoted by

(a) K, L, M, N …..    (b) a, b, c, d   …..   (c) A, B, C, D …..  (d) V, W, X, Y, Z….

(24) Maximum number of electrons, the third shell can accommodate is –

(a) 32   (b) 2  (c) 8   (d) 18

(25) A chlorine atom has _____ protons, ______electrons, _____ neutrons

(a) 18,17,18   (b) 17,18,18   (c) 17,17,18  (d) 17,17,17

(26) Sodium(Na+) has number of electrons –

(a) 10   (b) 11   (c) 12    (d)  9

(27) The scientist who measured the mass and charge of an electron was –

(a) Goldstein   (b) Rutherford    (c) Dalton     (d) Thomson

(28) Rutherford directed a stream of _____ on a thin gold leaf in the scattering experiment –

(a) alpha particles    (b) beta particles   (c) gamma particles   (d) X-rays

(29) By the experiments, Rutherford concluded that the positive charge of an atom is –

(a) spread all over the atom   (b) revolves around the atom in orbits  (c) exists in the empty space   (d) present in the nucleus

(30) Atomic number of an atom is –

(a) number of protons + number of neutrons   (b) number of neutrons  (c) number of electrons + number of protons  (d) number of protons

(31) In a neutral atom, the number of protons is equal to 

(a) number of neutron  (b) mass number   (c) number of electrons   (d) valancy

(32) Neutrons are discovered by –

(a) Joseph Thomson  (b) James chadwick   (c) Ernest Rutherford  (d) John Dolton

(33) The mass number of an atom is the sum of

(a) neutron and electron  (b)  neutron and proton  (c) proton and electron  (d) proton, neutron and electron

(34) The element with the same atomic number and mass number is –

(a) Hydrogen     (b) Deuterium   (c) Helium   (d) Oxygen

(35) Which of the following pairs are isotopes

(a) Helium and hydrogen   (b) Ice and Stream  (c)  Oxygen and Ozone (d) Hydrogen and deuterium

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