Structure Of The Atom Class 9 CBSE Notes - Chapter 4

Essentially, the structure of an atom comprises of protons, neutrons and electrons. These basic components provide the mass and charge of the atoms. The nucleus comprises of proton and neutron, with the electron orbiting around that.

The Structure of an Atom

Over the years, many models of atoms have been put forth based on theories and assumptions. But one of the many significant models includes the Bohr Model, Thomson’s Model and Rutherford’s Model. However, these are quite outdated today. The Bohr-Sommerfeld Theory is the most widely accepted model that explains the atomic structure. In this model, the concept of electrons revolving around orbits are completely scrapped, instead, electrons exist in “energy states.”

Atomic Number

Atomic number is also called as proton number, is the number of protons present inside the atom’s nucleus. This provides elements with the characteristic features that determine its place on the periodic table. For instance, hydrogen has an atomic number 1, due to the presence of only 1 proton in its nucleus. Uranium has an atomic number 92, as there are 92 protons present inside the nucleus.

Structure Of The Atom Class 9 – Questions

  1. Describe the properties of protons, neutrons and electrons.
  2. Why was J.J Thompson’s atomic model phased out?
  3. Explain the limitations of Rutherford’s atomic model.
  4. Explain Bohr’s atomic model.
  5. What is valency? Illustrate with an example.
  6. Define atomic number and atomic mass.

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