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NCERT solutions Science Textbook for Class 9 chapter 4 Structure of the Atom

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Chapter 4 - Structure of the Atom

Pages 54 - 55

Compare the properties of electrons, protons and neutrons.

Q 1 | Page 54 |

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

Q 2 | Page 54 |

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

Q 3 | Page 54 |

Describe Bohr’s model of the atom.

Q 4 | Page 54 |

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

Q 5 | Page 54 |

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

Q 6 | Page 54 |

Define valency by taking examples of silicon and oxygen.

Q 7 | Page 54 |

Explain Atomic number with examples.

Q 8.1 | Page 55 |

Explain Mass number with examples.

Q 8.2 | Page 55 |

Explain Isotopes with examples.

Q 8.3 | Page 55 |

Explain Isobars with examples.

Q 8.4 | Page 55 |

Give any two uses of isotopes

Q 8.5 | Page 55 |

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

Q 9 | Page 55 |

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

Q 12 | Page 55 |

Composition of the nuclei of two atomic species X and Y are 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?

Q 13 | Page 55 |

For the following statement, write T for ‘True’ and F for ‘False’.

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

Q 14.1 | Page 55 |

For the following statement, write T for ‘True’ and F for ‘False’.

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

Q 14.2 | Page 55 |

For the following statement, write T for ‘True’ and F for ‘False’.

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

Q 14.3 | Page 55 |

For the following statement, write T for ‘True’ and F for ‘False’.

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

Q 14.4 | Page 55 |

Put tick (✓) against correct choice and cross (×) against wrong choice in following question.

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

(a) Atomic nucleus

(b) Electron

(c) Proton

(d) Neutron

Q 15 | Page 55 |

Put tick (✓) against correct choice and cross (×) against wrong choice in following question.

Isotopes of an element have

(a) the same physical properties

(b) different chemical properties

(c) different number of neutrons

(d) different atomic numbers

Q 16 | Page 55 |

Put tick (✓) against correct choice and cross (×) against wrong choice in following question.

Number of valence electrons in Cl ion are:

(a) 16

(b) 8

(c) 17

(d) 18

Q 17 | Page 55 |

Which one 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

Q 18 | Page 55 |

Complete the following table.

Atomic number Mass number Number of Neutrons Number of protons Number of electrons Name of the Atomic species
9 - 10 - - -
16 32 - - - Sulphur
- 24 - 12 - -
- 2 - 1 - -
- 1 0 1 0 -
Q 19 | Page 55 |

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