Periodic trends describe systematic changes in atomic and chemical behavior across the periodic table. They help connect an element’s position with reactivity, bonding and material behavior.
Atomic radius
Atomic radius generally decreases across a period and increases down a group. The trend reflects changing nuclear charge and electron-shell structure.
Ionization energy
Ionization energy generally increases across a period and decreases down a group. Elements with low ionization energies tend to lose electrons more readily and display stronger metallic character.
Electronegativity
Electronegativity generally increases from left to right and from bottom to top, with fluorine among the most electronegative elements. Differences in electronegativity strongly influence bond type and chemical reactivity.
Metallic character
Metallic character is strongest toward the lower-left part of the table. Metals tend to conduct electricity and heat, deform plastically and form positive ions, although engineering behavior depends on structure and processing.
Why these trends matter
Periodic trends support first-pass reasoning about alloying, corrosion, oxidation, ionic compounds and semiconductor behavior, but quantitative design still requires measured property data and applicable standards.
