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Element Encyclopedia
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The Halogens
The Halogens are the elements in group 7 of the periodic table.
Halogens each have seven valence electrons, which is why they have similar chemical properties. They all form diatomic molecules. For example, F2, Cl2, Br2, and I2.
Halogen Molecular Structure
Halogens are non-metals with low melting / boiling points. The melting points and boiling points then increase as you go down the group. This is because of the increasing atom size, distance from the nucleus, and shielding effect of electrons.
It is the only group that includes elements that belong to all three classical states of matter: solid, liquid, and gas (at room temperature).
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The halogen elements are poisonous and all have a similar strong smell.
Physical Characteristics
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Reactivity
Fluorine is the most reactive halogen, as well as the most reactive non-metal in the periodic table.
The reactivity of the halogens decreases as you go down the group, due to the increasing atom size, distance from the nucleus, and shielding effect of electrons.
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Halogens react directly with metals to form metal halides or salts. They react best with the alkali metals.
Bonding
Halogens are diatomic, and since they are non-metals, they form covalent bonds.
Diatomic Covalent Bond
Halogens react well with the alkali metals. The chemical bond between non-metals and metals is an ionic bond. Halogens form ionic bonds with alkali metals.
Ionic Bond
Ion Formation
The ions of halogens have a single negative charge.
This is because since they have seven valence electrons, they need one more valence electron to achieve stability;
The alkali metals have one valence electron, so they react well with each other because the alkali metal gives it's valence electron to the halogen, so they both end with eight valence electrons.
The alkali metal loses an electron, and the halogen gains one electron.
Electrons are negative, so when the halogen gains the electron, it becomes a single negative ion.
CITATION:
Webmaster@chemicalelements.com, Y. B. (n.d.). Chemical Elements.com - Halogens. Retrieved December 27, 2016, from http://www.chemicalelements.com/groups/halogens.html
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BBC - GCSE Bitesize: The halogens. (n.d.). Retrieved December 27, 2016, from http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/periodic_table/group7rev1.shtml
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BBC Bitesize - GCSE Chemistry - Group 7 - the halogens - Revision 3. (n.d.). Retrieved December 27, 2016, from http://www.bbc.co.uk/education/guides/z3vwxnb/revision/3