Lecture: Atomic Structure - Protons, Electrons, and Neutrons
Introduction
- Everything is made up of atoms (e.g., salt, sugar, water, plants, animals, humans).
- Atoms are composed of three particles: proton, electron, and neutron.
Structure of an Atom
- Shape: Spherical, like a ball.
- Nucleus: Dense central part of the atom.
- Energy Levels/Shells: Fixed paths around the nucleus where electrons are found.
- Protons and neutrons reside in the nucleus.
- Electrons revolve around the nucleus, similar to how planets revolve around the sun.
Why Do Electrons Revolve Around the Nucleus?
- Proton: Positively charged particle.
- Electron: Negatively charged particle.
- Electrostatic Force: Attraction between protons and electrons causes electrons to revolve around the nucleus.
Role of Neutrons
- Neutron: Neutral particle (no charge).
- An atom as a whole is neutral because the number of protons equals the number of electrons (e.g., Hydrogen atom: 1 proton and 1 electron).
- Neutralization: Positive protons neutralize negative electrons.
Helium Atom Example
- Contains 2 protons in the nucleus and 2 electrons in the first shell.
- Like charges (protons) repel each other; neutrons prevent this repulsion by acting as insulation.
- Neutrons allow stable structure by minimizing repulsion between protons.
Lithium Atom Example
- Contains 3 protons in the nucleus and 3 electrons revolving around the nucleus.
- Shell/Energy Levels: K, L, M, N.
- First Shell: Holds 2 electrons.
- Second Shell: Holds remaining 1 electron, can accommodate up to 8 electrons.
- Multiple shells reduce repulsion among electrons.
Summary
- Atoms are made up of protons, electrons, and neutrons.
- Atoms are electrically neutral because the number of protons equals the number of electrons.
- Neutrons minimize repulsion among protons in the nucleus.
- Multiple shells in an atom reduce repulsion among electrons.
This concludes the lecture on Atomic Structure, Protons, Electrons, and Neutrons.