Key Concepts: Periodic Trends

Core Definitions

• Atomic Radius: Increases going DOWN a group (more energy levels) and DECREASES going across a period (more protons pull electrons closer).
• Ionization Energy: The energy required to remove an electron; INCREASES across a period and DECREASES down a group.
• Electronegativity: An atom's ability to attract electrons in a bond; INCREASES across a period and DECREASES down a group.
• Electron Affinity: The energy released when an atom gains an electron; generally increases across a period.
• Metallic Character: INCREASES going down a group and DECREASES going across a period.
• Fluorine: The most electronegative element on the periodic table.