Alkali Metal Properties

Alkali Metals Group (Todd Helmenstine)
This periodic table is highlighted to identify the alkali metals group of elements. (Todd Helmenstine)

The alkali metals are the elements located in group IA of the periodic table (the first column). The key characteristic these elements share in common is that they all have one electron in the outer electron shell. This lone electron is loosely bound, making this a set of reactive metallic elements.

List of the Alkali Metals

Note the element missing from most lists of alkali metals is hydrogen. Hydrogen is an alkali metal when it’s found in its metallic state. Under ordinary temperatures and pressures, hydrogen occurs as a gas and has the properties of a nonmetal.

Alkali Metal Properties

Rubidium Metal Sample ( Dnn87)
Like other alkali metals, rubidium is a shiny, silver-colored metal. The pure element reacts in air or water, so it’s kept in a sealed container.

The lone outer shell electrons leads the alkali metal elements to share several common properties:

  • The one outer electron is easily lost, forming the univalent (1+) cation (e.g., Na+).
  • Alkali metals are typically less dense than other metals.
  • Atoms of alkali metals have the largest atomic radii of elements in their periods.
  • Alkali metals are highly reactive elements. In particular, they readily react with halogens and other nonmetals. The pure metals react with oxygen in air and with water. As you move down the group, reactivity increases. A piece of sodium metal in water will burn; a piece of cesium metal in water will explode.
  • Atoms have low ionization energies.
  • Alkali metal atoms have low electronegativity values.
  • Unlike most metals, alkali metals tend to be soft and have low melting points. You can cut sodium metal with a butter knife. The melting point of cesium is low enough it will melt from the heat of your hand or in a warm room.
  • Like other metals, alkali metals tend to be shiny and metallic in appearance, as well as good conductors of electricity and heat.