What is the name for the group of elements that all have seven valence electrons?

The group of elements that all have seven valence electrons is known as the halogens. These elements, which include fluorine, chlorine, bromine, iodine, and astatine, are found in Group 17 of the periodic table. The defining characteristic of halogens is indeed their seven valence electrons, which contribute to their high reactivity as they seek to gain one more electron to achieve a stable octet configuration.

The other groups mentioned do not share this specific property. Noble gases, for example, are characterized by having a full set of eight valence electrons, making them chemically inert. Alkali metals have only one valence electron, while alkaline-earth metals possess two. Therefore, halogens are uniquely identified by their seven valence electrons, which significantly influences their chemical behavior and reactivity in various compounds.