chem lecture 2/2 6/3

Electron Models

• Electron Configuration: Describes how electrons are arranged in an atom (in shells, subshells, and orbitals).

• Historical Progression:

  • The Quantum Mechanical Model developed by Louis de Broglie in the late 1800s to 1980 explains electron paths in more complex mathematical ways compared to previous models.

  • Electrons are not in fixed orbits but exist in a 'cloud' around the nucleus as a probability distribution.

Quantum Mechanical Model of an Atom

• Electron Movement:

  • Electrons exhibit wave-like behavior and are found in regions of space known as orbitals.

  • Electrons are not confined to simple circular paths; rather, they occupy varying shapes of orbitals within subshells.

• Structure of Electron Orbits:

  • Atoms consist of electrons in energy levels (shells), which can contain multiple subshells.

    • Energy levels are defined as 1, 2, 3, ..., n.

  • Each energy level has a specific number of subshells:

    • Shell 1: 1s (1 subshell)

    • Shell 2: 2s, 2p (2 subshells)

    • Shell 3: 3s, 3p, 3d (3 subshells)

    • Shell 4: 4s, 4p, 4d, 4f (4 subshells)

Subshells and Their Capacities

• Subshells:

  • Designated by letters (s, p, d, f).

• Capacity of Each Subshell:

  • s: 2 electrons

  • p: 6 electrons

  • d: 10 electrons

  • f: 14 electrons

Filling Order of Electrons

• The order of filling subshells follows a specific sequence:

  • 1s → 2s → 2p → 3s → 3p → 4s → 3d

• Electrons fill the lowest energy levels first before moving to higher ones.

Example Electrons in Energy Levels

• Energy Level Capacities:

  • Level 1: 2 electrons (1s)

  • Level 2: 8 electrons (2s + 2p)

  • Level 3: 18 electrons (3s + 3p + 3d)

  • Level 4: 32 electrons (4s + 4p + 4d + 4f)

Electron Configuration Examples

Potassium (K)

• Atomic number: 19

• Electron Configuration:

  • Total electrons: 19

  • Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

Calcium (Ca)

• Atomic number: 20

• Electron Configuration:

  • Total electrons: 20

  • Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

Scandium (Sc)

• Atomic number: 21

• Electron Configuration Predictive Activity:

  • Participants write the electron configuration based on the knowledge of various configurations established.

Understanding Ions

• An ion is formed when an atom gains or loses electrons:

  • For example, sodium ion (Na⁺) loses one electron:

    • Original configuration: 1s² 2s² 2p⁶ 3s¹

    • Ion configuration: 1s² 2s² 2p⁶

  • Oxygen ion (O²⁻) gains two electrons:

    • Original configuration: 1s² 2s² 2p⁴

    • Ion configuration: 1s² 2s² 2p⁶ (like neon)

Emission Spectrum and Lab Report Overview

• Electrons can absorb energy and jump between energy levels, causing emission spectra observable in light.