The halogens are a group of elements in the periodic table. They are located to the right of the other nonmetals and to the left of the noble gases. Elements in the halogen group have seven electrons in their outer shells giving them many unique properties.
What elements are halogens?
The halogens include the five elements fluorine, chlorine, bromine, iodine, and astatine. They make up column 17 of the periodic table.
What are the similar properties of halogens?
Halogens share many similar properties including:
They all form acids when combined with hydrogen.
They are all fairly toxic.
They readily combine with metals to form salts.
They have seven valence electrons in their outer shell.
They are highly reactive and electronegative.
They all exist as diatomic molecules (two atoms) when in their pure form.
Phases Under Standard Conditions
Under standard conditions, the halogens exist in all three main phases of matter: Iodine and astatine are solids; bromine is a liquid; and fluorine and chlorine are gases. The only other element to be a liquid at room temperature is mercury.
Order of Abundance
All of the halogens can be found in the Earth's crust. Fluorine and chlorine are fairly abundant with iodine and bromine being somewhat rare. Astatine is extremely rare and is considered one of the rarest naturally occurring elements on Earth.
Here is the order of abundance in the Earth's crust:
Fluorine
Chlorine
Bromine
Iodine
Astatine
Interesting Facts about Halogens
The name halogen comes from the Greek words "hals", meaning "salt", and "gen", meaning "to make."
Fluorine is considered one of the most reactive elements in existence.
Simple compounds that contain halogens are called halides.
Fluorine gas is deadly. Breathing air with only a small concentration of 0.1% fluorine can cause death.
Small amounts of fluoride are used in water and toothpaste to help prevent tooth decay.
The first halogen to be isolated and recognized as an element was chlorine.
Astatine has found uses in medicine even though it is radioactive and decays quickly.
Bromine liquid evaporates easily at room temperatures emitting an orange vapor.
Bromine has a very strong and bad odor. It gets its name from the Greek word "bromos" which means "stench."
Despite the fact that fluorine and chlorine are poisonous, small amounts are essential to human health and life. Iodine is also needed for human health.
