Halogens – Properties and Elements
The halogens are a group of non-metallic elements located in Group 17 (Group VIIA) of the periodic table. The name "halogen" means "salt former" because these elements readily form salts when combined with metals. This group includes:
- Fluorine (F)
- Chlorine (Cl)
- Bromine (Br)
- Iodine (I)
- Astatine (At)
These elements share similar chemical properties and have seven valence electrons, making them highly reactive.
1. Fluorine (F)
- Atomic number: 9
- Discovered in 1886 by isolating it from hydrofluoric acid
- Most electronegative element
- Smallest atomic radius among the halogens
- Oxidation state: -1 (except in its elemental form where it's 0)
- Extremely reactive – reacts with nearly all elements including noble gases like Xenon to form compounds like XeF2
2. Chlorine (Cl)
- Atomic number: 17
- Discovered in 1774 by isolating it from hydrochloric acid
- Oxidation states: -1, +1, +3, +5, +7
- Exists as Cl-35 and Cl-37 isotopes
- Commonly found as sodium chloride (NaCl)
3. Bromine (Br)
- Atomic number: 35
- Discovered in 1826
- Only liquid non-metal at room temperature – reddish-brown in appearance
- Oxidation states: -1, +1, +3, +4, +5
- More reactive than iodine but less than chlorine
- Isotopes: Br-79 and Br-81
- Strong oxidizing agent and highly toxic
4. Iodine (I)
- Atomic number: 53
- Discovered in 1811 using seaweed and sulfuric acid
- Oxidation states: -1, +1, +5, +7
- Violet-colored solid at room temperature
- Stable isotope: I-127
5. Astatine (At)
- Atomic number: 85
- Discovered in 1940 via synthesis
- Radioactive with very short half-life (few hours)
- Oxidation states: -1, +1, +3, +5, +7
- Appears as a black, metallic-looking solid
- Does not exist naturally in large quantities
Tags
group 17 elements
halogen elements
Halogens
periodic table nonmetals
properties of fluorine chlorine bromine iodine astatine