Lecture on Electron Configurations

Overview

• Understanding electron configurations using Schrodinger's equation.
• Quantum numbers derived from Schrodinger's equation:
  • n: Principal quantum number.
  • l: Angular momentum quantum number.
  • mₗ: Magnetic quantum number.
  • mₛ: Spin quantum number.
• Pauli Exclusion Principle: No two electrons in an atom can have identical sets of four quantum numbers.

Quantum Numbers

• Principal Quantum Number (n): Indicates the energy level/shell.
• Angular Momentum Quantum Number (l): Defines the shape/subshell.
  • Values from 0 to n-1.
  • Each value of l corresponds to a sub-shell type (s, p, d, f).
• Magnetic Quantum Number (mₗ): Orientation of orbitals within a subshell.
  • Range from -l to +l.
• Spin Quantum Number (mₛ): Electron spin, values are +1/2 or -1/2.

Electron Population in Orbitals

• Electrons populate orbitals following the Pauli Exclusion Principle.
• Example: Helium in n=1, l=0 (s subshell) with opposite spins.
• Orbital Designations:
  • S orbitals: Spherical
  • P orbitals: Dumbbell-shaped, 3 orientations
  • D orbitals: More complex shapes, 5 orientations

Filling Order and Energy Levels

• Aufbau Principle: Fill from lowest to highest energy levels.
• Hund’s Rule: Maximize unpaired electrons in degenerate orbitals (same energy).
• Example:
  • Boron: 2p¹
  • Carbon: 2p² (filling unoccupied orbitals first)

Periodic Table and Electron Configurations

• Use periodic table as a guide for electron filling order.
• Note crossover: Fill 4s before 3d due to energy levels.
• Noble Gas Configuration: Shorthand notation using nearest noble gas as core.

Transition Metals and Anomalies

• D-block (transition metals): Inconsistent electron configurations.
• Chromium and Copper have exceptions due to stability of half-filled/full d orbitals.
• F-block (lanthanides and actinides): Follow similar principles but with more complex exceptions.

Practice Problem

• Example given for full and noble gas electron configurations.
• Indium: Full configuration reviewed with the noble gas shorthand using Krypton.

Tips and Tricks

• Use periodic table sections to infer electron configurations.
• Recognize consistent inconsistencies in transition elements.
• Remember the stability of half-filled/full d orbitals.

Participate in practice questions to solidify understanding. Feel free to reach out for further clarification!