Solution of Chapter 4. Structure of the Atom (NCERT - Science Book)

What are canal rays?

If an atom contains one electron and one proton, will it carry any charge or not?

On the basis of Thomson's model of an atom, explain how the atom is neutral as whole.

On the basis of Rutherford's model of an atom, which subatomic particle is present in the nucleus of an atom?

Draw a sketch of Bohr's model of an atom with three shells.

What do you think would be the observation if the a-particle scattering experiment is carried out using a foil of a metal other than gold?

Name the three subatomic particles of an atom.

Helium atom has an atomic mass of 4u and two protons in its nucleus. How many neutrons does it have?

Write the distribution of electrons in carbon and sodium atoms.

If K and L shells of an atom are full, then what be the total number of electrons in the atom?

How will you find the valency of chlorine, sulphur and magnesium?

If the number of electrons in an atom is 8 and the number of protons is also 8, then (i) what is the atomic number of the atom? And (ii) what is the charge on the atom?

With the help of Tab. Is given below, find out the mass numbers of oxygen and sulphur atoms:

For the symbols H, D and T, tabulate three subatomic particles found in each of them.

Write the electronic configuration of any one pair of isotopes and isobars.

Compare the properties of electrons, protons and neutrons.

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

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

Describe Bohr’s model of the atom.

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

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

Define valency by taking the examples of silicon and oxygen.

Explain with examples (i) Atomic number (ii) Mass number (iii) Isotopes, and (iv) Isobars. Give any two uses of isotopes.

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

If bromine is available in the form of, say, two isotopes 7935Br (49.7%) 8135Br (5,3%) calculate the average atomic mass of bromine atom.

The average atomic mass of a sample of an element X is 16.2 u. What are the percentages of isotopes and in the sample.

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

Composition of the nuclei of two atomic species X and Y is given as under:

X Y

Protons = 6 6

Neutrons = 6 8

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

For the following statements, write T for true and F for false:

J. J. Thomson proposed that the nucleus of an atom contains only nucleons.

For the following statements, write T for true and F for false:

A neutron is formed by an electron and a proton combining together. Therefore, it is neutral.

For the following statements, write T for true and F for false:

The mass of an electron is about 1/2000 times that of a proton.

For the following statements, write T for true and F for false:

A radioactive isotope of iodine is used for making tincture iodine, which is used as a medicine.

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

(a) Atomic nucleus (b) Electron

(c) Proton (d) Neutron

Isotopes of an element have :

(a) the same physical properties

(c) different number of neutrons

(b) different chemical properties

(d) different atomic numbers

Number of valence electrons in Cl- ion are:

(a) 16

(b) 8

(c) 17

(d) 18

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

(a) 2, 8 (b) 8, 2, 1

(c) 2, 1, 8 (d) 2, 8,1

Complete the following table: