CBSE Class 9 Science Structure of the Atom Quiz 1

1. Which of the following correctly represents 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 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?

A \(_{15}^{31}\)X B \(_{16}^{31}\)X C \(_{15}^{16}\)X D \(_{16}^{15}\)X

4. 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

5. The first model of an atom was given by

A N. Bohr B E. Goldstein C Rutherford D J. J. Thomson

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

A 3 B 7 C 1 D 4

7. Which of the following statement is always correct?

A An atom has equal number of electrons and protons. B An atom has equal number of electrons and neutrons. C An atom has equal number of protons and neutrons. D An atom has equal number of electrons, protons and neutrons.

8. Hydrogen exists in three isotopic forms, \(_{1}^{1}\)H, \(_{1}^{2}\)H, \(_{1}^{3}\)H known as protium, deuterium and tritium. Why are all the isotopes neutral in nature?

A Since neutrons are neutral in nature hence isotopes are electrically neutral. B All the isotopes have one electron and one proton, hence they are neutral. C All the isotopes have one proton and one neutron, hence they are neutral. D Increasing number of protons in the isotopes make them neutral.

9. How many electrons are present in M-shell of an element with atomic number 20?

A 5 B 8 C 12 D 18

10. There are two atomic species X and Y, such that

A X and Y are isobars. B X and Y have different chemical properties. C X and Y have different physical properties. D All of these.