Approx. 2000 times smaller than protons or neutrons.
Negatively charged (-1).
The Periodic Table
Each element is represented in a box as a nuclear symbol.
Elemental Symbol
Located on the right side in the box (e.g., Li for Lithium).
Atomic Number
Located at the bottom left.
Indicates the number of protons.
Determines the identity of the element.
Mass Number
Located at the top left.
Sum of protons and neutrons.
Number of electrons equals the number of protons in an atom.
Isotopes
Atoms with the same number of protons (same atomic number) but different numbers of neutrons.
Examples
Lithium-7: 3 protons, 4 neutrons.
Lithium-6: 3 protons, 3 neutrons.
Lithium-8: 3 protons, 5 neutrons.
Stability
Typically, only 1-2 isotopes of an element are stable.
Unstable isotopes decay by emitting radiation (alpha, beta, gamma) or neutrons.
Radioactive Decay
Unstable isotopes emit radiation.
Process leads to decay into other elements.
To be discussed further in a future video.
Electrons and Energy Levels
Electrons are arranged in shells, with each shell at a higher energy level as it moves away from the nucleus.
Electron Excitation
Electrons can jump to higher energy levels when they gain enough energy.
Energy is provided by electromagnetic radiation.
Electrons re-emit energy as they fall back to lower energy levels.
Ionization
When an electron absorbs enough energy to leave the atom, creating a positive ion.
Ionizing Radiation
Capable of knocking electrons off atoms, causing ionization.
Conclusion: This video covered the basics of atomic structure, isotopes, electron energy levels, and ionization. Stay tuned for more on radioactive decay in the next video.