Introduction
- The matter is composed of atoms and molecules.
- Earlier it was believed that the atom is indivisible.
- By the end of the nineteenth century, scientists revealed the presence of charged particles in an atom.
- Atoms are composed of 3 subatomic particles- electron, neutron and neutron.
- Electrons have a negative charge; protons have a positive charge and neutrons are neutral.
- The central hard part of an atom is the nucleus which contains protons and neutrons.
- Electrons are found moving around this nucleus in fixed circular orbits called shells or energy levels.
CLASS 9 CHAPTER 4
https://www.youtube.com/watch?v=VeNhu8pf4Qc&list=PLAVY2tu_2M4jDkdNv8QJLwQi0eQVJ4Ryd&index=7