* Similar Electron Configuration: They all have seven electrons in their outermost electron shell (valence shell), giving them a common electron configuration of ns²np⁵. This configuration makes them highly reactive and eager to gain one more electron to achieve a stable octet configuration like the noble gases.
* Nonmetals: They are all nonmetals, meaning they generally lack the characteristics of metals like malleability, ductility, and conductivity.
* Form Diatomic Molecules: They exist as diatomic molecules (F₂, Cl₂, Br₂, I₂) in their elemental state due to their strong tendency to form covalent bonds.
* Halogenation: They react with metals to form salts, a process called halogenation. This is a common characteristic of halogens, giving rise to their name, which comes from the Greek words "halos" (salt) and "genes" (born).
* Reactivity Trends: Their reactivity generally decreases as you move down the group. Fluorine is the most reactive halogen, followed by chlorine, bromine, and iodine. This trend is due to the increasing atomic size and decreasing electronegativity down the group.
In summary, these elements are placed in the same group because they have similar chemical properties arising from their similar electron configurations and their tendency to gain one electron to achieve a stable octet.
