NCERT Class-9 Science Solutions: Chapter 4-Structure of the Atom Part 6 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 30:

Match the names of the Scientists given in column A with their contributions towards the understanding of the atomic structure as given in column B

Match the Column a and Column B (Q)
(A)(B)
  1. Ernest Rutherford
  • Indivisibility of atoms
  • J. J. Thomson
  • Stationary orbits
  • Dalton
  • Concept of nucleus
  • Neils Bohr
  • Discovery of electrons
  • James Chadwick
  • Atomic number
  • E. Goldstein
  • Neutron
  • Mosley
  • Canal rays

Answer:

Match the Column a and Column B (A)
(A)(B)
  1. Ernest Rutherford
iii Concept of nucleus
  1. J. J. Thomson
iv Discovery of electrons
  1. Dalton
i Discovery of electrons
  1. Neils Bohr
ii Stationary orbits
  1. James Chadwick
vi Neutron
  1. E. Goldstein
vii Canal rays
  1. Mosley
v Atomic number

Question 31:

The atomic number of calcium and argon are 20 and 18 respectively, but the mass number of both these elements is 40. What is the name given to such a pair of elements?

Answer:

Isobars

Question 32:

Complete the Table on the basis of information available in the symbols given below

Element, Proton and Neutron (Q)
Element

Answer:

Element, Proton and Neutron (A)
Element
1718
66
3546

Question 33:

Helium atom has 2 electrons in its valence shell but its valency is not 2, Explain.

Answer:

Helium atom has 2 electrons in its outermost shell and its duplet is complete. Hence, the valency is zero.

Question 34:

Fill in the blanks in the following statements

  1. Rutherford՚s α-particle scattering experiment led to the discovery of the …
  2. Isotopes have same … but different …
  3. Neon and chlorine have atomic numbers 10 and 17 respectively. Their valencies will be … and … respectively.
  4. The electronic configuration of silicon is … and that of Sulphur is …

Answer:

  1. Rutherford՚s α-particle scattering experiment led to the discovery of the atom nucleus.
  2. Isotopes have same atomic number but different mass number.
Isotopes
  1. Neon and chlorine have atomic numbers 10 and 17 respectively. Their valencies will be 0 and 1 respectively.
  2. The electronic configuration of silicon is 2,8, 4 and that of Sulphur is 2,8, 6.