Overview
This lecture covers the basic structure of atoms, the behavior of subatomic particles, and the concept of electron shells and stability.
Atomic Structure
- Atoms are the basic unit of chemical elements.
- Atoms consist of a nucleus containing protons and neutrons, surrounded by an electron cloud.
- Protons have a positive charge; neutrons are uncharged; electrons have a negative charge.
- The number of protons equals the number of electrons, making atoms electrically neutral.
Electron Shells and Stability
- Electrons occupy rings or shells around the nucleus, each with a specific energy level.
- Each shell can hold a maximum number of electrons.
- Only electrons in the outermost shell (valence electrons) participate in chemical bonding.
- Atoms with a full outermost shell are stable; otherwise, they are chemically reactive.
Specific Examples
- Carbon: 6 protons, 6 neutrons, 6 electrons; electrons distributed in shells.
- Helium: 2 electrons in one shell (shell is full), making it stable and unreactive.
- Hydrogen: 1 electron in one shell (not full), making it reactive.
- Neon: 8 electrons in the outer shell, making it stable.
- Oxygen: 6 electrons in the outer shell, making it reactive.
The Octet Rule
- Atoms with more than one shell require 8 electrons in the outermost shell for stability (octet rule).
- Atoms with fewer than 8 valence electrons will share, gain, or lose electrons to achieve stability.
- Hydrogen and helium are exceptions to the octet rule, needing only 2 electrons for stability.
Key Terms & Definitions
- Atom — The fundamental unit of a chemical element.
- Proton — Positively charged particle in the nucleus.
- Neutron — Uncharged particle in the nucleus.
- Electron — Negatively charged particle surrounding the nucleus.
- Electron Shell — Energy level around the nucleus where electrons are found.
- Octet Rule — Atoms seek 8 electrons in their outermost shell for stability.
Action Items / Next Steps
- Review examples of atomic structures for hydrogen, helium, carbon, neon, and oxygen.
- Study the octet rule and its exceptions.