Periodic Table - Group 1 Elements

Group 1 metals all react with cold water, in some cases very violently indeed. The reaction produces hydrogen gas and the hydroxide of the metal, which is strongly alkaline, giving the group its alternative name, the alkali metals. The reactions are exothermic, in fact, the heat released during the reaction of potassium and water is sufficient to ignite the hydrogen gas given off. The periodic table is all about patterns; as you descend the group, the metals become more reactive.

The reason for this and other patterns is the electron configuration. Group 1 is so-called because each of the elements has a single outer electron. During chemical reactions, atoms will either gain electrons, lose electrons or share electrons in order to achieve the structure of the nearest noble gas. It is only the outer electrons that are involved. The options for the group one elements are to either gain seven electrons or lose one electron - the latter is easier and this is exactly what happens. Atoms are neutral, they have the same number of electrons as protons. Since the number of protons remains the same during reactions, this loss of an electron means after reacting, the group one metals end up as ions with one positive charge. The reason that they are more reactive as you go down the group is that the outer electron is further from the nucleus. This means that they are not held as tightly and can be more easily lost.