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CBSE - Class 9 Science Structure of the Atom Worksheet

Isotopes of an element have

the same physical properties

different chemical properties

different number of neutrons

different atomic numbers.

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

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.

Explain with examples iv) Isobars. Give any two uses of isotopes.

Describe Bohr’s model of the atom.

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

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

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

Define valency by taking examples of silicon and oxygen.

10.

Compare the properties of electrons, protons and neutrons.

11.

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.

12.

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

13.

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?

14.

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

15.

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

16.

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.

17.

$Na^+$ has completely filled $K$ and $L$ shells. Explain.

18.

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.

19.

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

Atomic Nucleus

Electron

Proton

Neutron

20.

If $Z = 3$, what would be the valency of the element? Also, name the element.

Worksheet Answers

15.

19.

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