Periodic Trends Atomic radii Ionization Energy Multiple Ionization Energy Electron Affinity Electronegativity

Atomic Radius Is an estimate of the size of an atom from its nucleus to its outer perimeter (measured in pm or 10-12 m) Trend: Increases to the left and down Reason: core charge increases across the period pulling electrons closer in and added shells increase distance and decrease pull

Ionization energy The energy needed to remove an electron from the gaseous atom. 1st ionization energy removes electron with the smallest amount of attraction to the nucleus The atom become a positive ion- cation when it loses an electron Ionization energy is measured in MJ/mol

Ionization energy (cont) Trend: Ionization energy increases as you go right and up Reason: atomic radius decreases, electrons are pulled in by greater nuclear charge Reason: atomic radius increases, pull by far away nucleus decreases as well as screening makes it easier to remove an electron

Electron Affinity Electron affinity is the energy released when an electron is added to a gaseous atom (measured in kJ/mol). The atom becomes a negative ion (anion) when it accepts an electron Trend: Electron affinity increases as you go right and up. Reason: Across a period, radius decreases, atomic charge increases, greater pull.

Electron affinity (cont) Trend: As you go down a group, electron affinity decreases Reason: Greater radius, decreased nuclear pull and electrons circling in far orbits make adding an electron not as desirable

Electronegativity Property that determines the relative strength of attraction by an atom of a bonding electron pair in a chemical compound F-F equal sharing of electrons in the covalent bond. H-F unequal sharing of electrons. Fluorine has a greater attraction and electrons stay closer to fluorine than hydrogen in the covalent compound.

Electronegativity (cont) Trend: Increases across a period Reason: core charge Trend: Decreases as you go down a group Reason: far orbits have a decreased attraction to far away nucleus

Multiple Ionization energy Every electron can be successively removed from an atom- 1st, 2nd, 3rd… ionization energy At each successive removal, ionization energy increases Trends are consistent with 1st ionization energy and the model of the atom