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CBSE - Class 9 Science Structure of the Atom Worksheet

Define valency by taking examples of silicon and oxygen.

Composition of the nuclei of two atomic species $X$ and $Y$ are given as under

Give the mass numbers of $X$ and $Y$. What is the relation between the two species?

Complete the following table.

Number of valence electrons in Cl ionis

The average atomic mass of a sample of an element $X$ is 16.2 u. What are the percentages of isotopes $^{16}_8X$ and $^{18}_8X$ in the sample?

For the following statements, write T for True and F for False.
(d) An isotope of iodine is used for making tincture iodine, which is used as a medicine.

What are the limitations of Rutherford’s model of the atom?

For the following statements, write T for True and F for False.
(c) The mass of an electron is about $\frac{1}{2000}$ times that of proton.

Explain with examples (i) Atomic number. Give any two uses of isotopes.

Describe Bohr’s model of the atom.

10.

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

Atomic Nucleus

Electron

Proton

Neutron

11.

Which one of the following is a correct electronic configuration of sodium?

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

12.

Explain with examples (iii) Isotopes. Give any two uses of isotopes.

13.

Explain with examples (ii) Mass number. Give any two uses of isotopes.

14.

Compare all the proposed models of an atom given in this chapter.

15.

Summarise the rules for writing of distribution of electrons in various shells for the first eighteen elements.

16.

Number of valence electrons in $Cl^-$ ion are:

17.

For the following statements, write T for True and F for False.
(b) A neutron is formed by an electron and a proton combining together. Therefore, it is neutral.

18.

What are the limitations of J.J. Thomson’s model of the atom?

19.

For the following statements, write T for True and F for False.
(a) J.J. Thomson proposed that the nucleus of an atom contains only nucleons.

20.

Compare the properties of electrons, protons and neutrons.

Worksheet Answers

10.

11.

16.

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