The document discusses several periodic properties of elements including atomic radius, ionization energy, and electronegativity. It explains that atomic radius decreases across a period as nuclear charge increases but increases down a group as electron shielding increases. Ionization energy generally increases across a period as it becomes harder to remove electrons but decreases down a group as electrons are farther from the nucleus. Electronegativity also increases across a period as nuclear attraction increases.

1. PERIODIC TABLE