Structure of the Atom Class 9 Questions

📝 Structure of the Atom 

Multiple Choice Questions 

1. Which of the following correctly represent the electronic distribution in the Mg atom?

(a) 3, 8, 1
(b) 2, 8, 2
(c) 1, 8, 3
(d) 8, 2, 2

2. Rutherford’s ‘alpha `(alpha)` particles scattering experiment’ resulted in the discovery of

(a) Electron

(b) Proton

(c) Nucleus in the atom

(d) Atomic mass

3. The number of electrons in an element X is 15 and the number of neutrons is 16. Which of the following is the correct representation of the element?

4. Dalton’s atomic theory successfully explained

(i) Law of conservation of mass

(ii) Law of constant composition

(iii) Law of radioactivity

(iv) Law of multiple proportion

(a) (i), (ii) and (iii)

(b) (i), (iii) and (iv)

(c) (ii), (iii) and (iv)

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

5. Which of the following statements about Rutherford’s model of atom are correct?

(i) considered the nucleus as positively charged

(ii) established that the `alpha`–particles are four times as heavy as a hydrogen atom

(iii) can be compared to the solar system

(iv) was in agreement with Thomson’s model

(a) (i) and (iii)

(b) (ii) and (iii)

(c) (i) and (iv)

(d) only (i)

6. Which of the following are true for an element?

(i) Atomic number = number of protons + number of electrons

(ii) Mass number = number of protons + number of neutrons

(iii) Atomic mass = number of protons = number of neutrons

(iv) Atomic number = number of protons = number of electrons

(a) (i) and (ii)

(b) (i) and (iii)

(c) (ii) and (iii)

(d) (ii) and (iv)

 7. In the Thomson’s model of atom, which of the following statments are correct?

(i) the mass of the atom is assumed to be uniformaly distributed over the atom

(ii) the positive charge is assumed to be uniformaly distributed over the atom

(iii) the electrons are uniformaly distributed in the positively charged sphere

(iv) the electrons attract each other to stabilise the atom

(a) (i), (ii) and (iii)

(b) (i) and (iii)

(c) (i) and (iv)

(d) (i), (iii) and (iv)

8. Rutherford’s `alpha`–particle scattering experiment showed that

(i) electrons have negative charge

(ii) the mass and positive charge of the atom is concentrated in the nucleus

(iii) neutron exists in the nucleus

(iv) most of the space in atom is empty

Which of the above statements are correct?

(a) (i) and (iii)

(b) (ii) and (iv)

(c) (i) and (iv)

(d) (iii) and (iv)

9. The ion of an element has 3 positive charges. Mass number of the atom is 27 and the number of neutrons is 14. What is the number of electrons in the ion?

(a) 13

(b) 10

(c) 14

(d) 16

10. Identify the `Mg^{2+}` ion from Fig. where n and p represent the number of neutrons and protons respectively

11. Elements with valency 1 are

(a) always metals

(b) always metalloids

(c) either metals or non-metals

(d) always non-metals

12. The first model of an atom was given by

(a) N. Bohr

(b) E. Goldstein

(c) Rutherford

(d) J.J. Thomson

13. An atom with 3 protons and 4 neutrons will have a valency of

(a) 3

(b) 7

(c) 1

(d) 4

14. The electron distribution in an aluminium atom is

(a) 2, 8, 3

(b) 2, 8, 2

(c) 8, 2, 3

(d) 2, 3, 8