The energy needed to remove an electron from a neutral atom in its gas state.

Family which has an oxidation number of +2, very reactive.

Due to stability in valence shells, in what direction does ionization energy generally decrease among periods (rows)?

Non-metallic family whose elements can exist at all three states of matter at room temperature; neither very reactive nor unreactive, most have an oxidation number of -1.

Due to electron shielding, in what direction does ionization energy generally increase among groups (columns)?

Very reactive elemental family made of metals that do not occur normally in nature; softer than most metals, good conductors of heat and energy.

The elemental family with the highest ionization energy.

Family who's elements have an oxidation number of 0; stable because of full valence shells.

Changes in ionization energy are directly linked with another trend which is:

Respectively, at what states do these elements stay in at room temperature? Chlorine, Astatine, and Bromine