Ionization Energies and Electron Affinities
* Electron affinities marked with an asterisk (*) have been obtained from theoretical calculations rather than experimental measurements. The heavy colored line separates metals (ionization energyThe quantity of energy required to remove an electron from a neutral atom or molecule or from a positive ion. usually below about 800 kJ mol–1) from nonmetals.
This table gives ionization energies and electron affinities for common elements, and displays the information in terms of the periodic tableA chart showing the symbols of the elements arranged in order by atomic number and having chemically related elements appearing in columns.. Ionization energies are in black, with electron affinities in red. For ionization energies, two general tendencies arise. First, as one moves down a given groupThose elements that comprise a single column of the periodic table. Also called family. in the periodic table, the ionization energy decreases. Second, as one moves from left to right across the periodic table (from an alkaliAny substance in aqueous solution that is bitter, irritating to the skin, and has a pH value greater than 7.0.-metal atomThe smallest particle of an element that can be involved in chemical combination with another element; an atom consists of protons and neutrons in a tiny, very dense nucleus, surrounded by electrons, which occupy most of its volume. to a noble gasOne of the elements in the same column of the periodic table as helium; also called inert gas.), the ionization energy increases on the whole. While electron affinities display fewer regularities on the table, trends do exist. All the halogens have values of about 300 kJ mol–1 while the group VI nonmetals have somewhat lower values, in the region of 200 kJ mol–1 or less.