Overview
This lecture explains how to write electron configurations for elements, including both full and condensed forms, with step-by-step examples from each block of the periodic table.
Electron Configuration Basics
- Electron configuration shows how electrons are arranged in atomic orbitals for an element.
- There are four subshells: s, p, d, and f.
- s subshell: 1 orbital, holds up to 2 electrons.
- p subshell: 3 orbitals, holds up to 6 electrons.
- d subshell: 5 orbitals, holds up to 10 electrons.
- f subshell: 7 orbitals, holds up to 14 electrons.
Periodic Table Blocks
- s block: first two groups and helium.
- p block: right side of the table.
- d block: inner transition metals.
- f block: elements in the two bottom rows.
Writing Electron Configurations
- Always start from hydrogen and move left to right across the periodic table to the desired element.
- The order of filling orbitals (Aufbau principle) is crucial.
- s block example (Beryllium): 1s² 2s ².
- p block example (Sulfur): 1s² 2s² 2p⁶ 3s² 3p⁴.
- d block example (Iron): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶ (note: d block’s number is one less than the period).
- f block example (Plutonium): 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 4f¹⁴ 5d¹⁰ 6p⁶ 7s² 5f⁶ (note: f block’s number is two less than period).
Condensed (Shorthand) Electron Configurations
- Use the noble gas from the previous row as a placeholder in brackets.
- For sulfur: [Ne] 3s² 3p⁴.
- For iron: [Ar] 4s² 3d⁶.
- For plutonium: [Rn] 7s² 5f⁶.
Key Terms & Definitions
- Electron Configuration — The arrangement of electrons in an atom’s orbitals.
- Subshell (s, p, d, f) — Types of orbitals with specific shapes and electron capacities.
- Block — Sections of the periodic table based on subshell filling.
- Condensed/Shorthand Configuration — A shorter way to write electron configurations using noble gas notation.
Action Items / Next Steps
- Practice writing full and condensed electron configurations for various elements.
- Review the periodic table’s blocks and subshell order.
- Watch the suggested practice quiz video for step-by-step answers.