Periodic trends Tamil revision mind map presented as four horizontal directional gauges: atomic radius decreasing across a period and increasing down a group, first ionisation energy increasing across a period with dips at magnesium to aluminium and phosphorus to sulphur due to subshell and half-filled stability, electronegativity increasing across a period and decreasing down a group with fluorine highest at four point zero, and electron affinity magnitude generally increasing across a period with chlorine's more negative value than fluorine's explained by fluorine's small size causing extra electron-electron repulsion.