NCERT Class 9 Science Structure Of The Atom Questions

STRUCTURE OF THE ATOM

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 (α) particles scattering experiment’ resulted in to discovery of

(a) Electron

(b) Proton

(c) Nucleus in the atom

(d) Atomic mass

3. 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)

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

(i) considered the nucleus as positively charged

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

(iii) can be compared to 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)

5. One electron is present in the outer most shell of the atom of an element X. What would be the nature and value of charge on the ion formed if this electron is removed from the outer most shell? 

6. In the atom of an element X, 6 electrons are present in the outermost shell. If it acquires noble gas configuration by accepting requisite number of electrons, then what would be the charge on the ion so formed?

7. In response to a question, a student stated that in an atom, the number of protons is greater than the number of neutrons, which in turn is greater than the number of electrons. Do you agree with the statement? Justify your answer.

8. The atomic number of calcium and argon are 20 and 18 respectively, but the mass number of both these elements is 40. What is the name given to such a pair of elements?

9. Helium atom has 2 electrons in its valence shell but its valency is not Explain.

10. An element X has a mass number 4 and atomic number 2. Write the valency of this element?

11. Why do Helium, Neon and Argon have a zero valency?

12. Enlist the conclusions drawn by Rutherford from his α-ray scattering experiment.

13. In what way is the Rutherford’s atomic model different from that of Thomson’s atomic model?

14. What were the drawbacks of Rutherford’s model of an atom?

15. What are the postulates of Bohr’s model of an atom?

16. Show diagramatically the electron distributions in a sodium atom and a sodium ion and also give their atomic number.

Please refer to attached file for NCERT Class 9 Science Structure Of The Atom Questions