CBSE Class 9 Science Structure of the Atom MCQs Set A

Answer: C

Question:  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 

Answer: B

Question: An element has electronic configuration 2,8,4 it will be classified as
(A) Metal
(B) Non metal
(C) Metalloid
(D) None of these

Answer: C

Question: 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

Answer: B

Question: 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 

Answer: C

Question: Cathode rays have
(A) Mass only
(B) Charge only
(C) Both mass and charge
(D) Neither mass nor charge

Answer: C

Question: Which of these is a pairs isobar ?
(A) 6C12, 8O16
(B) 6C13, 6C14
(C) 20Ca40, 18Ar40
(D) None of these

Answer: C

Question: 7N15 and 8O16 are a pair of
(A) Isotopes
(B) Isobars
(C) Isotones
(D) None of these 

Answer: C

Question: The nucleus of the hydrogen atom is called as
(A) Neutron
(B) Electron
(C) Proton
(D) Nucleons 

Answer: C

Question: 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 

Answer: B

Question: 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 

Answer: A

Question: Isotopes differ in
(A) No. of electrons
(B) No. of protons
(C) No. of neutrons
(D) Chemical reactivity 

Answer: C

Question: 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 

Answer: D

Question: 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

Answer: B

Question: 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 

Answer: B

Question: a particle is emitted by 92X238 during redioactivity. The new specie y should be :
(A) 90Y234
(B) 90Y238
(C) 92Y234
(D) 94Y234 

Answer: A

Question: 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

Answer: C

Question: If the nuclide of actinium 89Ac228, emits b particle, the daughter nuclide will be
(A) 88Ra228
(B) 90Th228
(C) 87Fr224
(D) 90Th229

Answer: B

Question: 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

Answer: C

Question: The energy associated with an orbit
(a) increases with his distance from the nucleus
(b) decreases with increase in the distance from nucleus
(c) remains constant whatever may be the distance
(d) none of these   

Answer: A

Question:  The orbits are numbered by
(a) 100, 200, 300....
(b) 10, 20, 30....
(c) 1, 2, 3, 4....
 (d) 5, 10, 15....

Answer: C

Question:  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,....

Answer: A

Question:  The shell which has two electrons is
(a) first shell
(b) second shell
(c) third shell
(d) fourth shell

Answer: A

Question:  Maximum number of electrons, the third shell can accommodate is
(a) 32
(b) 2
(c) 8 
(d) 18 

Answer: D

Question:  In general, the nth shell can accommodate_____ electrons where ‘n’ stands for number of the shell.
(a) 3n^₂ 
(b) 2n²
(c) n² 
(d) 2n 

Answer: B

Question:  The distribution of _____ in various orbits of an atom is called electronic configuration of element
(a) neutrons
(b) protons
(c) electrons
(d) all of these 

Answer: C

Question:  The electronic configuration of oxygen
(a) 2, 7
(b) 2, 6
(c) 2, 4, 2
(d) 4, 4 

Answer: B

Question:  2, 8,1 is the electronic configuration of
(a) lithium
(b) potassium
(c) helium
(d) sodium 

Answer: D

Question:  Number of electrons in the outermost shell of carbon is
(a) 4
(b) 6
(c) 3
(d) 8 

Answer: A

Question:  Total number of electrons in an atom of nitrogen is
(a) 9
(b) 6
(c) 8
(d) 7 

Answer: D

Question:  The noble gases from the following are
(a) O_2, N₂, H₂ 
(b) Cl, F, Br
(c) He, Ne, Ar
(d) Na, K, Ca

Answer: C

Question:  Noble gases do not react with other elements to form compounds because
(a) they are unstable
(b) they are gases
(c) they are stable
(d) they are already compounds

Answer: C

Question:  In a chemical reaction, ___________ participate.
(a) valence electrons
(b) all electrons of the atom
(c) protons
(d) electrons and protons

Answer: A

Question: The valency of an element is its
(a) electronic configuration
(b) combining capacity
(c) atomic number
(d) mass number

Answer: A

Question:  Atoms combine to attain stable configuration by
(a) sharing electrons
(b) sharing, accepting or donating electrons
(c) donating electrons
(d) accepting electrons

Answer: B

Question:  A chlorine atom has ____ protons, _____ electrons and _____ neutrons.
(a) 18, 17, 18
(b) 17, 18, 18
(c) 17, 17, 18
(d) 17, 17, 17 

Answer: C

Question:  The number of electrons shared between two oxygen atoms is
(a) 2
(b) 1
(c) 2
(d) 4 

Answer: D

Question: . The number of electrons shared by each chlorine atom to form a molecule is
(a) 2
(b) 1
(c) 3
(d) 7 

Answer: B

Question:  In a CO₂ molecule, the total number of electrons shared between a carbon and two oxygen atoms are
(a) 8
(b) 4
(c) 2
(d) 6

Answer: B

Question:  In the formation of NaCl, sodium atom
(a) receives an electron
(b) shares an electron
(c) does not react
(d) donates an electron 

Answer: D

Question:  Sodium ion (Na+) has ____ number of electrons
(a) 10
(b) 12
(c) 11
(d) 13 

Answer: A

Question:  When chlorine atom becomes chloride ion it
(a) loses an electron gains an electron
(b) gains an electron
(c) electrostatic force
(d) magnetic force

Answer: B