Atomic Structure and Concepts of Chemistry

# Review of Atomic Structure and Chemistry Concepts

## Structure of the Atom
- **Nucleus**: The central part of the atom containing protons and neutrons.
  - **Protons**: Positively charged particles (+1 charge) with a relative mass of 1.
  - **Neutrons**: Neutral particles with no charge and a relative mass of 1.
- **Electrons**: Negatively charged particles (-1 charge) orbiting the nucleus in shells; about 2000 times smaller than protons or neutrons.

## Understanding the Periodic Table
- **Nuclear Symbol**: Representation of each element in the periodic table.
  - **Element Symbol**: Symbol for the element (e.g., Li for Lithium).
  - **Atomic Number**: Number of protons in the atom, determining the element.
  - **Mass Number**: Total number of protons and neutrons in the atom.
- **Example with Lithium**:
  - Atomic number: 3 (3 protons).
  - Mass number: 7 (3 protons + 4 neutrons).
  - Number of electrons equals the number of protons (3 electrons for lithium).

## Isotopes
- Atoms of the same element with the same number of protons but different numbers of neutrons.
- Examples of Lithium Isotopes:
  - **Lithium-6**: 3 protons, 3 neutrons.
  - **Lithium-7**: 3 protons, 4 neutrons.
  - **Lithium-8**: 3 protons, 5 neutrons.
- Stability:
  - Usually, only one or two isotopes of an element are stable.
  - Unstable isotopes decay, emitting radiation (alpha, beta, gamma) or neutrons.
  - This process is known as radioactive decay.

## Electron Energy Levels
- **Energy Levels (Shells)**: Electrons are arranged in shells around the nucleus.
  - Shells further from the nucleus have higher energy levels.
- **Excitation of Electrons**:
  - Electrons can move to higher energy levels if they absorb enough energy, becoming excited.
  - Absorption of energy requires specific amounts of electromagnetic radiation.
  - Excited electrons eventually return, re-emitting energy.

## Ionization
- **Ionization Process**:
  - An electron absorbs sufficient energy to leave the atom, creating a positive ion.
  - The atom is left with more protons than electrons, thus a positive charge.
- **Ionizing Radiation**: Radiation capable of removing electrons from atoms, causing ionization.

## Conclusion
- This lecture covered the fundamental aspects of atomic structure, isotopes, electron behavior, and ionization. For further details on radioactive decay, stay tuned for upcoming videos.