Microsoft Word - WaterChemistry

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Element Allotropes

Tin:

 grey tin (alpha tin)

 white tin (beta tin)

 rhombic tin (gamma tin)

 sigma tin

Iron:

 ferrite (alpha iron) - forms below 770°C (the Curie point, TC); the iron

becomes magnetic in its alpha form; BCC

 beta - forms below 912°C; BCC crystal structure

 gamma - forms below 1,394°C; FCC crystal structure

 delta - forms from cooling down molten iron below 1,538°C; BCC

crystal structure

 epsilon - forms at high pressures

Lanthanides and Actinides
 Cerium, samarium, terbium, dysprosium and ytterbium have three allotropes.
 Praseodymium, neodymium, gadolinium and terbium have two allotropes.
 Plutonium has six distinct solid allotropes under "normal" pressures. Their
densities vary within a ratio of some 4:3, which vastly complicates all kinds of
work with the metal (particularly casting, machining, and storage). A seventh
plutonium allotrope exists at very high pressures. The transuranium metals Np,
Am, and Cm are also allotropic.
 Promethium, americium, berkelium and californium have 3 allotropes each.