What are Halogens?
Halogens are a group of chemical elements in the Periodic Table. The word “halogen” comes from the term “salt-producing”. These Periodic elements are named Halogens, because of their ability to produce a wide variety of salts when they react with metallic elements. All Halogen elements are located in group 17 in the Periodic Table and they vary in physical and chemical properties. Halogen elements are the following 5 chemical elements: Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At).
Physical Characteristics of the Halogens
When it comes to physical characteristics of Halogen elements in the Periodic Table it’s noteworthy to mention that this is the only group of chemical elements in the entire Periodic Table to feature elements in the three main physical states at standard temperature – the solid, liquid and gaseous states. Their overall density is relatively low. As the Halogens’ atomic numbers progress further down the Periodic Table their melting point and boiling point increase significantly, as well as their covalent radius, while their electronegativity and first ionization energy show a sufficient decrease in numbers. Their atomic masses vary between 18 and 210.
Chemical Properties of the Halogens
Halogen elements bear some similarities between each other when it comes to their chemical properties. For example, each Halogen element forms acids when it’s bonded to the chemical Hydrogen. Halogens are reactive to metals and they form a large variety of salts, including sodium chloride, which is also known as common table salt. Halogens are toxic, but their reactivity decreases as their atomic numbers increase further down the Periodic Table. Since Halogens have a high electronegativity and a high nuclear charge, they are highly reactive. Halogens have a total of 7 valence electrons in the outermost electron shell.
Bonding and reaction to other elements and compounds
Since Halogen elements are highly reactive they have the ability to react and form other elements and compounds with various chemical elements in the Periodic Table. For example, they form various salts when exposed to metallic elements. Halogens also form isotopes. Iodine alone has 38 various isotopes. When Halogens are exposed to Hydrogen, they form hydrogen halides. The hydrogen halides formed by Fluorine and Chlorine are highly acidic. All Halogens in the Periodic Table can react to Sodium, forming sodium halides. These chemical elements also form a variety of interhalogen compounds, organohalogen compounds, and polyhalogenated compounds. Halogens can also react to water. Fluorine has a vigorous water reaction, which produces hydrogen fluoride and oxygen. Chlorine forms acids when exposed to water, as does Bromine. Iodine, on the other hand, has a slim to none reaction to water.
Uses and applications of Halogens
Halogens find a large application in medicine, disinfectants, and lighting installations. Some of them play a valuable biological role for humans and other types of organisms.
Bromine and Chlorine are used in a large variety of disinfectants – they can be found as vital compounds in products for swimming pools, bleach, medicine, and so on. They are effective when it comes to getting rid of germs and bacteria. Halogen elements are also used in the manufacturing of halogen lamps and halogen incandescent light bulbs. Astatine is used in nuclear medicine and cancer treatment. While Iodine poses risk of breast cancer and stomach cancer, it finds application in some medicines. Fluorine is used in steel manufacturing, in refrigerant gases, and as an essential compound in many polymers.
Halogens on Earth
Most Halogen elements in the Periodic Table are quite common on Earth and its biological organisms. Fluorine and Chlorine are among the most common elements on our planet. Bromine doesn’t occur in its natural state and it’s commonly found in bromide salts in rocks. Iodine occurs naturally and there are two natural Iodine sources on Earth, which are used for commercial purposes – one in Chile and the other one is in the US. Astatine is among the rarest naturally occurring elements on Earth and it can be derived from several naturally occurring Astatine isotopes.