Electron Configuration and Quantum Numbers

Warm Up Activity

• The activity encourages the definition of the mass number of an element.
• Determine the atomic number of calcium.
• Calculate the number of neutrons in silicon.

Learning Goals

• Recognize and compare the relative energies of s, p, and d orbitals.
• Use the Aufbau principle, Hund's rule, and Pauli exclusion principle to determine electron configurations.

Success Criteria

• Compare and rank the relative energies of s, p, and d orbitals and explain their significance.
• Construct full and condensed electron configurations for elements and ions up to Z=36.

Electron Configurations

• Shows where the electrons are located within an atom.
• Each energy level or shell surrounding an atom is given a letter (s, p, d and f).
• Each orbital can hold up to 2 electrons
• Breakdown of each energy level capacity:
  • s sublevel has 1 orbital and can hold 2 electrons.
  • p sublevel has 3 orbitals and can hold 6 electrons.
  • d sublevel has 5 orbitals and can hold 10 electrons.
  • f sublevel has 7 orbitals and can hold 14 electrons.

Principles of Electron Configurations

• Electron configurations are based on three primary principles:
  • Aufbau principle
  • Pauli exclusion principle
  • Hund's rule

Aufbau Principle

• Electrons occupy the lowest energy orbitals (or shells) first.
• Principle energy level (n = 1,2,3,...) corresponds to the energy levels of an electron within an atom.

Electron Configuration Details

• Each principal energy level is divided into sub-levels (e.g., s, p, etc).
• Electrons are found within specified orbitals in each sublevel.
• The order of energy levels and sublevels when creating an electron configuration is 1s² → 2s² → 2p⁶ → 3s² → 3p⁶ → 4s² → 3d¹⁰ → 4p⁶.

Electron Configuration of Silicon

• Silicon has 14 electrons.
• Its full electron configuration begins at 1s.
• Sub-levels:
  • s contains 1 orbital and starts at the 1st principal energy level.
  • p contains 3 orbitals and starts at the 2nd principal energy level.
  • d contains 5 orbitals and starts at the 3rd principal energy level.
  • f contains 7 orbitals and starts at the 4th principal energy level.

Sub-levels

• s sub-levels:
  • Contains 1 orbital
  • Is spherical shaped.
  • Starts at the 1st principal energy level.
• p sub-levels:
  • Contains 3 orbitals.
  • Has 3 different tear shapes.
  • Starts at the 2nd principal energy level.
• d sub-levels:
  • Contains 5 orbitals.
  • Has 5 different shapes.
  • Starts at the 3rd principal energy level.
• f sub-levels:
  • Contains 7 orbitals.
  • Has 7 different shapes.
  • Starts at the 4th principal energy level.
• Each orbital holds 2 electrons.

Check-in Questions

• "If each orbital (region of space) can hold a maximum of 2 electrons, determine how many electrons can fit in:"
  • "The s orbital"
  • "The p orbitals"
  • "The d orbitals"
  • "The f orbitals"

Practice Question

• Write the electron configuration of the following elements:
  • Sodium
  • Magnesium
  • Boron
  • Neon
  • Sulfur

Periodic Table Layout

• The energy sublevel filled (or partially filled) last will align with the location of that element within the periodic table.
• Example:
  • Phosphorus is located in the p block and therefore the electron configuration should end at 3p.
  • P=15: 1s²2s²2p⁶3s²3p³

Magnesium Electron Configurations

• Can be written as 1s²2s²2p⁶3s².
• They can also be written as condensed electron configurations: [Ne]3s².
• Rule:
  • Check for the closest noble gas (Check to the left of the element).
  • Write this in square brackets and then state the location of the remaining outer electrons in the atom.
• Electron configuration for Chlorine:

Aufbau/ Orbital Diagrams

• A visual representation of electron configurations.
• Provide more specific information to the individual electrons involved.
• Each square represents an orbital and sublevels that contain more than one orbital appear together.
• Example: d sublevels contain 5 orbitals, so there will be 5 squares.

Pauli Exclusion Principle

• Each orbital can hold a maximum of two electrons, meaning an orbital can contain 0, 1, or 2 electrons.
• Each electron appears to be spinning on an axis.
• Spin can only be in two directions, represented as up and down arrows (↑↓).
• The first electron that will enter the orbital is drawn as an upwards pointing half-arrow and the second electron must have an opposing direction to the first electron.

Hund's Rule

• One electron enters each orbital until each contain an electron with the same spin direction.
• After each orbital contains one electron of the same spin, a second electron in the opposite direction can enter any of the orbitals.

Explore the principles governing electron configurations, including the Aufbau principle and Hund's rule. Learn to determine the electron configurations of elements and ions. Understand the relationship between orbital types and electron capacity.