3.-Electron-Configuration---Ionisation-energies

Electron Configurations and Diagrams

  • Overview: The structure of the periodic table is organized into periods (vertical) and groups (horizontal).

Understanding Electron Behaviour

  • Electron Nature: At A-level, electrons are considered a cloud of negative charge rather than a distinct particle, occupying an atomic orbital defined by specific energy levels.

  • Atomic Orbitals: Vary in energy and shape across energy levels.

Electron Configuration

  • Definition: Describes the arrangement of electrons in an atom.

  • Sub-shells: Comprised of:

    • s: Holds 2 electrons

    • p: Holds 6 electrons

    • d: Holds 10 electrons

    • f: Holds 14 electrons

  • Orbitals: Each orbital holds up to 2 electrons, depicted using half arrows.

Filling the Orbitals

  • Filling Rules:

    1. Lower energy orbitals fill first.

    2. Orbitals fill singly before pairing up.

    3. No orbital holds more than two electrons.

    4. 4s fills before 3d.

Transition Elements

  • Energy Level Changes: Prior to scandium, 4s orbitals are lower in energy than 3d; after scandium, 3d becomes lower in energy.

  • Ionization of Transition Metals: When forming ions, transition metals lose 4s electrons before 3d electrons.

Box-and-Arrow Diagrams

  • Representation: Diagrams use boxes for orbitals and arrows for electrons.

  • Examples:

    • Lithium (Li): 2,1

    • Oxygen (O): 2,6

    • Calcium (Ca): 2,8,8,2

Practice and Questions

  • Students are encouraged to practice writing the electron configurations for various elements (e.g., Magnesium, Aluminium, Arsenic).

  • Review the correct understanding of the periodic table regarding electron configurations.