Periodic Trends

Atomic Radius Measured between the radii between two atoms

Ionic Radius Cations are smaller than their corresponding atoms. Anions are larger than their corresponding atoms.

Trends in the periodic table: Atomic radius Radius DECREASES as you go left to right across a period.

Why?

Going across the period Electrostatic attraction increases. Electrons are pulled closer to the nucleus. Valence electrons are more tightly held.

Trends in the periodic table: Atomic radius Radius INCREASES as you go top to bottom down a group.

Why?

Going down a group Orbitals are larger. Electrons are farther from the nucleus. Valence electrons are less tightly bound.