Topic overview

Start with the big picture

Block assignment begins with the subshell filled last: s-block elements occupy Groups 1–2, p-block elements Groups 13–18, d-block elements Groups 3–12, and f-block elements sit in the table’s two detached rows. Their configurations and properties differ. The s and p blocks make up the main-group elements, while d-block transition elements commonly show variable oxidation states, colored compounds, catalytic activity, and complex-ion formation. The f block comprises lanthanides and actinides, with characteristic magnetic and oxidation-state features. Across the blocks, reactivity, atomic radius, ionization energy, and electronegativity show patterns alongside important irregularities. Understanding both the classification principle and these comparisons provides a foundation for interpreting periodic behavior.