Summary of Key Periodic Trends Shielding is constant Atomic radius decreases Ionization energy increases Electronegativity/Affinity increases Nuclear charge increases Metal Reactivity decreases Non-Metal Reactivity increases Metal Reactivity increases/non-Metal decreases Electronegativity/Affinity decreases Ionization energy decreases Nuclear charge increases Atomic radius increases Shielding increases Ionic size increases 1A 2A 3A 4A 5A 6A 7A Ionic size (cations) Ionic size (anions) decreases decreases