Halogens - Periodic Table - ChemTalk
Halogens - Periodic Table - ChemTalk
Halogens - Periodic Table - ChemTalk
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Halogen means “salt-producing”. They are salt-producing, because when they react with metals (often violently),
they produce ionic compounds known as salts. In 1811 John Schweigger wanted to name the element chlorine
“halogen”, but he failed. In 1826, Swedish chemist Jons Berzelius coined the term halogen for the entire group of
elements. The Greek word “hal”, meaning salt, also appears in the name of the mineral halite, aka sodium chloride.
Fluorine is the most reactive of all elements, and can only be stored in metals that form passivation layers of the
fluoride salt. These unique properties are because of the 7 electrons in their valence shell. Because of their
reactivity, there are almost never found in nature in their elemental form.
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Moving down the column, halogens increase in atomic radius as they add additional electron shells. In the
elemental state, they form diatomic molecules, joined by nonpolar covalent bonds. The fluorine-to-fluorine bond is
the weakest
The boiling points also increase due to increased Van Der Waals forces. So fluorine is a gas, and iodine is a solid. It
is the only group on the periodic table that has elements in the solid, liquid and gas phase at room temperature. All
of the halogens have a high electronegativity, but it decreases as you move down the column. In fact, fluorine has
the highest electronegativity of any element.
The ionization energy also decreases as you move down, making it easier to form higher oxidation states. The first
ionization energy of fluorine is so high, that it does not exhibit any positive oxidation states.
The halogens all have an interesting color, which can change depending on the medium or what it is dissolved in,
see a detailed explanation here.
Halogen Chemistry
The halogens react violently with alkali metals, alkaline earth metals, and aluminum, especially when there is a large
surface area of metal. They also form anions like the hypochlorite, chlorate, perchlorate, and bromate ions that are
very strong oxidizing agents. Fluorine commonly occurs in minerals like fluorite, CaF2. Halogens also form many
different interhalogen compounds, for example IF7, iodine (VII) fluoride.
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Further Reading
Alkali metals
Alkaline earth metals
Transition metals
Periodic Table with Element Names
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