Page 17 - Curriculum Visions Dynamic Book

In see Indium Iodine (I)
Element 53. Iodine is a violet-coloured nonmetallic element and one of the halogens in group 7 in the PeriodicTable.Although it is the least reactive of the common halogens, it is still very reactive and forms compounds with most other elements.
Its compounds can be processed to
make pure, dark violet crystals. At room temperature solid iodine turns into a vapour (it sublimes) to produce an unpleasantly irritating violet-coloured vapour.
Geology
Iodine does not occur as a native element. It is found in sea water and accumulates in seaweeds. It
is also found in some evaporite deposits
in association with other salts and is sometimes recovered from salt wells.
Biology
Iodine is one of the essential nutrients in the body. Lack of iodine causes thyroid problems.To ensure that people get enough of
it, iodine is added to most table salt.A solution
of iodine in alcohol (tincture of
iodine) is used as a disinfectant for wounds. Iodine
vapour is harmful.
Violet iodine crystals sublimating into iodine vapour.
Key facts...
Name: iodine
Symbol: I
Atomic number: 53
Atomic weight: 126.90
Position in Periodic Table: group 7 (17)
(halogens); period 5
State at room temperature: solid Colour: violet
Density of solid: 4.93 g/cc
Melting point: 113.7°C
Boiling point: 184.3°C
Origin of name: from the Greek word
iodes, meaning violet
Shell pattern of electrons: 2–8–18–18–7
Discovery
It was discovered in seaweed by Bernard Courtois in France in 1811.
Technology
It is used in medicine (a dilute solution of iodine in alcohol is called tincture of iodine and
is applied as an antiseptic),
in photography, and in colour dyes.
For more on iodine, see Volume 14: Chlorine, Fluorine, Bromine, and Iodine in the Elements set.
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