Structure of the Atom MCQ Science Class 9

MCQ Questions for Class 9 Science Chapter 4 Structure of the Atom with Answers

Q1. E. Goldstein in 1886 discovered the presence of new radiations in a gas discharge and  called them :- 

a)  a-particles ray

b) electron rays

c) cathode rays

d) canal rays

Ans :- canal rays 

Q2. The Proton’s is approximately ___________ as that of the electron.

a) 1000 times

b) 1500 times

c) 2000 times

d) None of these 

Ans :- 2000 times 

Q3. What are canal rays ?

a) Positively charged radiations

b) Negatively  charged radiations 

c) Neutral radiations

d) None of the above

Ans :- Positively charged radiations

Q4. Who was the first scientist to propose the model for the structure of the atom ? 

a) J.J. Thomson 

b) E. Rutherford 

c) Neils Bohr

d) All of them

Ans :- J.J. Thomson 

Q5. According to Thomson’s model an atom is similar to that of :- 

a) Christmas pudding 

b) Watermelon

c) Both (a) and (b)

d) None (a) and (b)

Ans :- Both (a) and (b)

Q6. Which of the following statements is true about Thomson’s model of an atom ? 

i) The mass of the atom is assumed to be uniformly distributed over the atom.

ii) The electrons attract each other to stabilize the atom.

iii) The electrons are uniformly distributed in the positive charge  sphere 

iv) The positive charge is assumed to be uniformly distributed over the atom.

a) (i), (ii) and (iii) are true 

b) (ii), (iii) and (iv) are true

c) (i), (iii) and (iv) are true

d) (i), (ii) and (iv) are true

Ans :- (i), (iii) and (iv) are true

Q7. Why is the atom electrically neutral by Thomson’ model ?

a) because positive charges are high in magnitude.

b) because negative and positive charges are  equal in magnitude.

c) because neutron are neutral 

d) None of these

Ans :- because negative and positive charges are  equal in magnitude.

Q8. ________ are studded in the positively charged sphere, like the seeds in the watermelon.

a) Electrons 

b) Protons

c) Neutrons

d) All of these

Ans :- Electrons

Q9. What are Alpha-particles 

a) singly-charged helium ions and having mass of 2u

b) neutral helium ions and having mass of 3u

c) Doubly-charged helium ions and having mass of 4u

d) None of these

Ans :- Doubly-charged helium ions and having mass of 4u

Q10. Rutherford’s alpha-particle scattering experiment was responsible for the discovery of 

a) Protons

b) Electrons

c) Nucleus

d) None of these

Ans :- Nucleus

Q11. Which facts of the atom does the Rutherford’s alpha-particle experiment shows us :- 

i) The mass and the positive charge of the atom is concentrated in the nucleus 

ii) Neutron exists in the nucleus

iii) Most of the space ie empty in the atom

iv) Electron have negative charge 

a) (i) and (ii) is showed by the experiment

b) (i) and (iv) is showed by the experiment

c) (ii) and (iii) is showed by the experiment

d) (i) and (iii) is showed by the experiment

Ans :- (i) and (iii) is showed by the experiment

Q12. Rutherford calculated the radius of the nucleus is about _______ less than the radius of the atom.

a) 10³ times

b) 10⁵ times  

c) 10⁷ times 

d) 10⁹ times

Ans :- 10⁵ times

Q13. All mass of an atom resides in the ________.

a) nucleus

b) Protons

c) Electrons

d) All of these

Ans :- nucleus

Q14. Which of the following conclusions of Rutherford’s experiment is true ?

a) most of the space inside the atom is empty 

b) the positive charge of the atom occupies very little space 

c) all the positive charge and the mass of the gold atom work concentrated in a very small volume within the atom

d) All of these 

Ans :- All of these 

Q15. Which of the following statements is true about the nuclear model of an atom ?

a) the electrons revolve around the nucleus in circular paths

b) the size of the nucleus is very small as compared to the size of the atom 

c) In atom the positively charged nucleus has all masses of that atom

d) All of these 

Ans :- All of these 

Q16. Most of the fast moving alpha-particles _____________ through the gold foil.

a) were deflected by small angles 

b) were deflected by big angles

c) passes straight 

d) were rebound 

Ans :- passes straight 

Q17. Surprisingly, In the experiment of Rutherford’s model, One out of every _____________ appeared to rebound.

a) 12000 particles

b) 2000 particles 

c) 1200 particles 

d) None of these

Ans :- 12000 particles

Q18. Which of the following statements is correct/true about Rutherford’s model of an atom?

i) It was in agreement with E. Goldstein

ii) It can similar to the solar system

iii) considered that the nucleus is Positively charged

iv) Established that the Alpha-particles are four times heavier as hydrogen atom

a) (i) statement is correct

b) (ii) and (iii) statement are correct

c) (i) and (iii) statement are correct

d) (ii) and (iv) statement are correct

Ans :- (ii) and (iii) statement are correct

Q19. Any particle in a circular orbit would undergo ________ 

a) change in state 

b) free fall 

c) acceleration

d) none of the above

Ans :- acceleration

Q20. While revolving in discrete orbits the electrons do not ________.

a) radiate power

b) radiate particles

c) radiate energy 

d) All of these

Ans :- radiate energy

Q21. The maximum number of electrons that can be accommodated in the outermost orbit is :-

a) 8 electrons

b) 18 elections

c) 32 electrons

d) It can be infinite electrons

Ans :- 8 electrons

Q22. What are Neutrons ?

a) subatomic particle which have charge and mass equal to the atomic number

b) subatomic particle which have no charge and mass nearly equal to the mass of protons 

c) subatomic particle which have no charge and mass nearly equal to the mass of electrons

d) none of the above 

Ans :- subatomic particle which have no charge and mass nearly equal to the mass of protons 

Q23. What are valence electrons ?

a) the electrons present in the innermost shell of an atom 

b) the electrons present in the outermost shell of an atom

c) the electrons present in the middle shell of an atom

d) none of these 

Ans :- the electrons present in the outermost shell of an atom

Q24. What is the Valency of phosphorus (P) ?

a) 3 valency

b) 5 valency

c) none (a) and (b)

d) both (a) and (b)

Ans :- both (a) and (b)

Q25. An atom of each element has a definite combining capacity is called its :-

a) octet power 

b) valence electrons

c) valency

d) none of these

Ans :- valency

Q26. What is an atomic number ?

a) total number of neutrons present in nucleus 

b) total number of protons present in nucleus 

c) total number of electrons present in nucleus 

d) none of the above

Ans :- total number of protons present in nucleus

Q27. The mass number of an atom is defined as :-

a) sum of the total number of electrons and neutrons present in the nucleus of an atom

b) sum of the total number of protons and electrons present in the nucleus of an atom

c) sum of the total number of protons and neutrons present in the nucleus of an atom

d) none of these

Ans :- sum of the total number of protons and neutrons present in the nucleus of an atom

Q28. Which statement is true about the ‘Isotopes’ :- 

i) the atoms of the same element, having same atomic number but different mass number

ii) the atoms of the different element, having different atomic number but same mass number

iii) they have different chemical properties but same physical properties

iv) they have same chemical properties but different physical properties

a) (i) and (ii) are true

b) (ii) and (iii) are true 

c) (ii) and (iv) are true

d) (i) and (iv) are true 

Ans :- (i) and (iv) are true statement 

Q29. What are the uses of isotopes?

a) An isotope of uranium is used as a fuel in nuclear reactors.

b) An isotope of cobalt is used in the treatment of cancer.

c) An isotope of iodine is used in the treatment of goitre.

d) All of the above 

Ans :- All of the above

Q30. Isobars are defined as :-  

a) Atoms of different elements with different atomic numbers, which have the same mass number

b) Atoms of different elements with same atomic numbers, which have the same mass number

c) Atoms of same element with same atomic number but different mass number

d) None of the above

Ans :-  Atoms of different elements with different atomic numbers, which have the same mass number

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