Halogens: Properties of Halogens

Halogens are a group of non metallic elements that are placed in Group 17 of the Periodic Table. There are 5 elements that are considered to be a part of this group, and that are widely known as halogens. These elements are Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I), and Astatine (At). Being members of the same elemental group, they show a lot of similar halogens properties, but there are some differences as well. The term halogens loosely implies 'salt former', and compounds that contain halogens are commonly referred to as salts. Learn more about the history of the periodic table.

If you are considering the physical forms in which these elements are present, you will find a great degree of variation. Chlorine and fluorine are primarily gases, iodine is found in solid forms, and bromine is one of the two elements that are present in the liquid state at room temperature. (The other one being mercury. Read more about mercury: the element). Astatine is also present in the solid state, but since it is highly radioactive it has been extremely difficult to observe its properties. There are 7 electrons present in the outer shell of halogens, and as a result they have an oxidation number of -1, which makes them very volatile elements. Read the following to learn more.

• Iodine: The Element
• Bromine: The Element
• Facts About Chlorine
• Bromine vs Chlorine

Chemical Properties of Halogens
Here are a few chemical properties of halogens that are easily observed in the elemental group.

High Electron Affinity
Out of all the halogens properties, this is perhaps the easiest to observe. Halogens are known to have very high degrees of electron affinity. As a result, their ability to gain electrons is very high. This fact makes halogens a very reactive group of elements, and many believe that halogens are the most reactive family of elements found in nature. Learn more about chemical elements.

Low Dissociation Energy
Along with high electron affinities, another one of the halogens properties that have been seen is that they have low dissociation energies. This implies that they can easily break up, or dissociate, into atoms and then combine with other substances. Both these halogens properties, make this elemental family highly reactive and volatile, especially with alkali metals and alkaline earths. Fluorine is considered to be one of the most reactive elements, and can also be toxic and highly corrosive.

Hydrogen Halides
When halogens react with hydrogen, they form binary compounds known as hydrogen halides. These hydrogen halides are extremely strong acids and this is one of the halogens properties which makes them a very unique brand of elemental family. When these hydrogen halides are converted to an aqueous state, they are known as hydrohalic acids.

Diatomic
In their purest form, halogens are always found to be diatomic in nature. What this means is that their molecules exist with two atoms each. The strongest form of chemical bonds that can exist between two substances is an ionic bond. And the most intriguing of all halogens properties is that when halogens combine or react with metals, they form ionic bonds. As a result of these reactions halogens become anions, or negatively charged ions. Owing to their highly reactive nature and the presence of several volatile halogens properties, halogens are never found in a pure form in nature. They must be extracted from their sources, using proper methods and techniques. Read about the uses of the following halogens.

• Fluorine Uses
• Bromine Uses
• Iodine Uses

Physical Properties of Halogens
As mentioned earlier, the physical state of existence of halogens is varied. They are found in all three states of existence. Here are some other physical properties of halogens that make them a very unique family of elements.

Appearance
Appearance wise fluorine exists as a pale yellow gas that is poisonous in nature, while chlorine is similarly poisonous but exists as a pale green colored gas. Iodine is commonly found as a black shiny piece of solid, and upon heating it forms a violet vapor. Lastly, bromine brownish liquid is extremely volatile in nature and is also considered toxic.

Diatomicity
At room temperature, halogens are diatomic in nature, as has already been mentioned earlier. Also, as you descend down the periodic table you will find that the melting point, the boiling point, the atomic radii and the ionic radii all increase in each subsequent element.

Here are some more halogens properties that you may find useful and informative.

Element/Properties	F	Cl	Br	I
Atomic Number	9	17	35	53
Relative Atomic Mass	19.99	35.45	79.90	126.90
Boiling Point/K	85.01	239.18	331.93	457.50
Density/kg m-3	1.696	3.214	7.50	4930

These were some common halogens properties, both chemical and physical in nature. The uses of halogens are manifold for industrial purposes. Out of all the families of elements found in the table, halogens are possibly one of the most important. Due to the halogens properties displayed by them, here are some purposes that halogens are generally used for - oxidizing agents, etching glass, chlorinating drinking water, manufacturing insecticides, bleaching wood pulp for making paper and also as an oxidant in matches and fireworks.