Which group of elements are known for having one valence electron and being very reactive?

The alkali metals are well-known for having one valence electron in their outermost shell, which significantly contributes to their high reactivity. This single valence electron is easily lost during chemical reactions, allowing them to form positive ions with a +1 charge. The strong tendency to lose this electron creates a rapid reaction with other elements, particularly nonmetals.

Alkali metals are located in Group 1 of the periodic table and include elements such as lithium, sodium, and potassium. Their reactivity increases as you move down the group, due to the increasing atomic size that makes it easier for the outermost electron to be lost.

In contrast, alkaline earth metals, which are found in Group 2, have two valence electrons and are less reactive than alkali metals. Transition metals are characterized by their ability to form various oxidation states and have more complex electron configurations, making their reactivity different from that of alkali metals. Halogens, located in Group 17, have seven valence electrons and are highly reactive, but their reactivity is due to their need to gain one electron to complete their octet, rather than losing one like alkali metals.