iodine

Name iodine
Symbol I
Atomic Weight 126.90447
Atomic Number 53
CAS ID 7553-56-2
Group Number 17
Group Name Halogen
Period Number 5
Origin of Name Greek, iodes = "violet."
Year Discovered 1811
Discovery Credits Discovered by B. Courtois at Paris, France.
Class Non-Metallic
Color Violet-Dark Gray, Lustrous
Standard State Solid at 77 F & 298 K
Description Black, shiny non-metal solid, I2. Sublimes easily. Used in disinfections, pharmaceuticals, food supplements, dyes, catalysts and photography.

Diagnostic tests: 
Iodine salts (along with F, Cl, and Br) will give a blue color to flames when heated on a copper disk.
Treatment of the salt with concentrated H2SO4 acid will effervesce with the evolution of a violet, sharp smelling gas (l2). Iodine is sometimes found associated with chlorine or bromine so a precipitate with AgNO3 solution is white (AgCl), cream (AgBr), or yellow (AgI) depending on which anion predominates. The precipitate is soluble in NH4OH.

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