The periodic table and periodic trends

The periodic table arranges elements by their number of protons and groups elements with similar patterns of outer electrons into the same column, which is why elements in the same column tend to have similar chemical properties. Properties change in predictable, repeating patterns: moving across a row from left to right, atomic radius generally decreases while ionization energy (how hard it is to remove an electron) and electronegativity (how strongly an atom attracts shared electrons) generally increase, and moving down a column reverses those trends. Reactivity follows too: alkali metals become more reactive moving down their column, while halogens become less reactive. These trends let chemists predict an unfamiliar main-group element's properties from its position on the table.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report