neet most important short notes (structure of atom) chemistry

The structure of an atom describes how an atom is made up of smaller particles called subatomic particles. Main Parts of an Atom 1. Nucleus The center of the atom is called the nucleus. It contains: Protons → positively charged particles (+) Neutrons → particles with no charge (0) The nucleus is very small but contains almost all the mass of the atom. 2. Electrons Electrons are negatively charged particles (−). They move around the nucleus in fixed paths or shells/energy levels. Charges of Subatomic Particles ParticleChargeLocationProton+1NucleusNeutron0NucleusElectron−1Around nucleus Simple Atomic Model Nucleus at the center Electrons revolving around it This model was explained by scientists like Ernest Rutherford and Niels Bohr. Example: Hydrogen Atom A hydrogen atom has: 1 proton 1 electron Usually 0 neutrons Important Points Atomic number = Number of protons Mass number = Protons + Neutrons In a neutral atom: Number of protons = Number of electrons Basic Representation Electron ○ ───────── ● ← Nucleus If you want, I can also explain: Bohr’s atomic model Thomson, Rutherford and Bohr models comparison Electronic configuration Structure of atom class 9 notes