* Energy Levels: Electrons occupy specific energy levels within an atom. Lower energy levels are closer to the nucleus and are more stable.
* Sublevels: Within each energy level are sublevels, denoted by letters: s, p, d, and f. Each sublevel has a slightly different energy level.
* S vs. P: The s sublevel is lower in energy than the p sublevel within the same principal energy level. This means that an electron will fill the s orbital before it fills the p orbital.
Example:
* In the second energy level (n=2), the 2s orbital is lower in energy than the 2p orbitals. Therefore, the 2s orbital fills before the 2p orbitals.
Visual Representation:
You can visualize this using a diagram called an orbital energy diagram. The diagram shows the relative energy levels of the orbitals. The s orbitals are always lower than the p orbitals within the same energy level.
Key Points:
* Aufbau Principle: This principle states that electrons fill orbitals in order of increasing energy.
* Hund's Rule: Electrons will individually occupy orbitals within a sublevel before pairing up.
* Pauli Exclusion Principle: No two electrons in an atom can have the same set of four quantum numbers (including spin).
By following these principles, you can predict the electron configuration of any atom.
