Halógeno

Halógeno is a term derived from Greek words meaning "salt-former." It refers to a group of chemical elements belonging to Group 17 of the periodic table. These elements are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). While technically all these are halogens, astatine is radioactive and extremely rare, so fluorine, chlorine, bromine, and iodine are the most commonly discussed.

Halogens are highly reactive nonmetals. They exist as diatomic molecules in their elemental form, meaning they consist of two atoms bonded together, such as F2, Cl2, Br2, and I2. Their reactivity stems from having seven valence electrons, just one electron short of a stable electron configuration. This makes them eager to gain an electron, either by forming ionic bonds with metals or covalent bonds with other nonmetals.

When halogens react with metals, they form salts, hence the name "salt-former." For example, sodium chloride (NaCl), common table salt, is formed from the reaction of sodium (a metal) and chlorine (a halogen). Similarly, they readily react with hydrogen to form hydrogen halides, such as hydrogen chloride (HCl) and hydrogen fluoride (HF). These can then dissolve in water to form hydrohalic acids.

The physical properties of halogens vary significantly down the group. Fluorine is a pale yellow gas, chlorine is a greenish-yellow gas, bromine is a reddish-brown liquid, and iodine is a dark purple solid that sublimes into a violet gas. Their melting and boiling points increase as the atomic number increases.