Iodine is a
nonmetallic halogen element in Group 17 of periodic table; atomic number 53;
atomic mass 126.9; melting point ca 114 C; boiling point ca 184 C; specific
gravity 4.93 g/cm3; oxidation states: 7,5,1,-1; [Kr] 4d10 5s2 5p5. Iodine is a
nearly black poisonous, corrosive solid at room temperature and readily sublimes
to a deep violet vapour, the colour of which is responsible for its name from
Greek. It is insoluble in water, soluble in common solvents. Iodine is required
in small amounts in human body for the function of the thyroid gland. Iodine
forms many important compounds of iodine such as iodine(V)oxide, potassium
iodide, iodine trichloride and iodoform of an Iodine containing organic
compound.
The related name, iodate indicates any salt of iodic acid containing the IO3-
radical; KIO3 (potassium iodate) and NaIO3 (sodium iodate) are the most
important salts. Whereas, iodide indicates any compound of iodine with a more
electropositive element or group such as such as CH3CH2I or any binary compound
of iodine which may contain the I- radical and which may be considered to be
derived from hydriodic acid (HI); KI and NaI are examples.
Inorganic iodide compounds are soluble in
water and hygroscopic except a few inorganic iodides such as copper iodide.
Their refractive indexes and specific gravities are higher than the
corresponding chlorine and bromine analogues. The important iodides commercially
are potassium iodide (KI), sodium iodide (NaI), hydrogen iodide (HI), and
polyiodides.
Lithium
Iodide (LiI; LiI·3H2O) white to
yellowish solid; soluble in water, alcohol; there are commercially anhydrous form
(melts at 446 C) and trihydrate form ( loses water at 72 C); It is used in
organic synthesis, manufacturing medicines and mineral waters. It is used in
electochemicstry (batteries and electrolytes) and redox
reactions.
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