Electron Configuration and Orbitals

Orbitals

• Atomic Orbital

  • a region of space in which there is a high probability of finding an electron

  • there are four orbitals: s, p, d, f

    • they are found in different energy levels called principle quantum numbers

• S Orbital

  • spherical shape and can only have 2 electrons

  • first to be filled when writing electron configurations

  • only one orientation

  • found in all energy levels

• P Orbital

  • looks like a peanut

  • has 3 orientations and can therefore hold 6 electrons

  • found in energy levels 2 - 7

• D Orbital

  • double peanut

  • can hold 10 electrons

  • has 5 orientations

  • found in energy levels 3-6

• F Orbital

  • flower shape

  • can hold 14 electrons

  • has 7 orientations

  • found in energy levels 4 and 5

Important Principles and Rules

• Aufbau Principle

  • The Aufbau Principle states that electrons occupy the lowest energy orbitals first before moving to higher energy orbitals. This means that when an atom is being filled with electrons, they will fill the s orbitals first, followed by p, d, and f orbitals in order of increasing energy.

• Pauli Exclusion Principle

  • The Pauli Exclusion Principle states that no two electrons in an atom can have the same set of four quantum numbers. This means that each electron must occupy a unique state within an orbital. In practice, this often translates to a maximum of two electrons per orbital, with one having a spin of +1/2 and the other a spin of -1/2.

• Hund’s Rule

  • Hund’s Rule states that electrons will occupy degenerate orbitals (orbitals of the same energy level) singly before pairing up. This means that for orbitals that are equal in energy, one electron will go into each orbital before any orbital gets a second electron. This helps minimize electron-electron repulsion and stabilizes the atom's structure.