Periodic Trends

Atomic Radius

The size of an atom; increases down a group (more electron shells) and decreases across a period (more nuclear pull); increases toward Francium.

Ionization Energy

The energy required to remove an electron from an atom; decreases down a group (electrons are farther from nucleus) and increases across a period; increases toward Helium.

Ion Formation

Atoms gain/lose electrons to get to a noble gas configuration; metals lose electrons (positive ion) and nonmetals gain electrons (negative ion).

Ion Atomic Radius

Relative to the original ion, positive ions are smaller and negative ions are larger.

Electronegativity

The ability of an atom to attract electrons in a bond; decreases down a group and increases across a period; increases toward Fluorine.

Electron Affinity

The attraction for an electron; generally becomes more negative across a period and less negative down a group; increases (more negative) toward Fluorine.

Melting Point

The temperature at which a substance changes from solid to liquid; varies by group, decreases down metals and increases down nonmetals

Boiling Point

The temperature at which a substance changes from liquid to gas; decreases down metals and increases down nonmetals

Density

The mass per unit volume of an element; generally increases down a group (heavier atoms)

Reactivity

How readily an element reacts; increases down metals (toward Francium) and up nonmetals (toward Fluorine).