Periodic Trends

Review The elements of the P. T. are placed into: rows by the number of energy levels they have. groups by the number of valence electrons they have. blocks by what kind of sublevel they are filling. Atoms can gain or lose electrons. Metallic atoms lose e- and form cations. Nonmetallic atoms gain e- and form anions.

Metallicity More Metallic Less Metallic Less Metallic More Metallic

The Big Questions What is atomic radius? How is ionic radius related to atomic radius? What is the trend concerning atomic radius? What is ionization energy, and what trend is associated with it? What is electronegativity, and what trend is associated with it?

Atomic Radius Atomic radius – distance from center of atom to outer electrons. Decreases across a period. Increases down a group.

Atomic Radii in Period 2 Li Be B C F N O Increasing atomic number Ne Increasing atomic number means greater attraction for electrons!

Atomic Radii of the Halogens Cl Br I At Increasing number of energy levels means a larger atom.

Atomic Radii General Trend Radius Increases Radius Decreases Radius Decreases Radius Increases

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

Ionic Radius

Ionization Energy Ionization Energy – energy required to remove 1 electron from an atom.

Ionization Energy +

Ionization Energy Increases across a period. Decreases down a group.

Electronegativity Electronegativity (EN) - Tendency of an atom to attract electrons in a chemical bond. Increases across a period. Decreases down a group. Excludes noble gases.

Electronegativity