gen-define-the-periodic-trends-and-give-one-short-worked-example-f3d2

Define the periodic trends and give one short worked example.

# Periodic Trends ## Key Definitions **Periodic trends** are predictable patterns in element properties that occur across periods (rows) and down groups (columns) of the periodic table. ### Main Trends: 1. **Atomic Radius**: Distance from nucleus to outermost electrons - **Increases** down a group (more electron shells) - **Decreases** across a period (stronger nuclear pull, same shell) 2. **Ionization Energy**: Energy needed to remove an electron - **Decreases** down a group (electrons farther from nucleus) - **Increases** across a period (stronger nuclear attraction) 3. **Electronegativity**: Ability to attract electrons in a bond - **Decreases** down a group - **Increases** across a period 4. **Metallic Character**: How readily an element loses electrons - **Increases** down a group - **Decreases** across a period --- ## Worked Example **Question**: Arrange these elements in order of increasing ionization energy: Na, Mg, Al, K **Solution**: - **K** (Group 1, Period 4): Largest atom, electron farthest from nucleus → **lowest IE** - **Na** (Group 1, Period 3): Smaller than K but still Group 1 - **Mg** (Group 2, Period 3): More protons than Na, stronger pull - **Al** (Group 13, Period 3): *Exception* - slightly lower than Mg (3p¹ easier to remove than 3s²) **Answer**: K < Na < Al < Mg (Note: Al < Mg is an exception due to subshell configuration)