The Allotropes of Selenium

I'm not sure what that means, but I need all of the allotropes of Selenium. Really soon. :( (Before Thursday, October 7, 9:00 pm Easter time) Please help.

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an allotrope is nothing more than a different form of the pure material.....Just as pure carbon can be both graphite and diamond. To get you started in the right direction, when I clicked on Se on this website, the crystal structure told me "monoclinic". There you can see the basic single "unit cell", and where all the atoms sit in their little box. Certain elements like to sit in those cells differently, and thats what your looking for.

So #1 monoclinic
#2 trigonal

*trigonal I found by google. good luck

Now that you know that allotrope are different configurations of elements with different physical properties like diamond and graphite (allotropes of C) or tin whose allotropes are "white" (the metallic form) and grey (a grey powder), all you have to do is click on Se in the periodic chart on this site and it will tell you about two different colors of Se.

You're luck you don't have to deal with phosphorus.

Now try it. It's on top of this page. Good luck to you. (The ads usually appear as the Selenium)

Martin you have it backwards. Any gray/black powder we almost always consider as metallically or semi-metallically bonded. Any rainbow color, or white powder as ionically/covalently bonded. Its just a rule of thumb.

If I synthesize say LaCrO3, it should be a brown/greenish color. After I anneal at 1200C, it turns to a black/gray color, which tells me it now possesses metallic bonding and is conductive! (what I'm looking for) If it doesn't change, its a high insulator and I messed up somewhere.

What is 'rainbow-coloured powder'? Does that mean powder with the colours of a rainbow or powder with any of the colours in the rainbow?

ANY color of the rainbow. Green, Red, Blue, etc.

How about... If it is transparent...?

No, I don't have it backwards. "White tin" is the metallic form and it isn't a powder, its the shiny metal we all know and love; grey tin is the amorphous powder; the conversion is spontaneous at, if I recall, 18 C. This process is called "tin pest" because the tin seems to be eaten away. Modern chemistry has been able to explain this alchemical mystery.

I don't work much with the semimetallics, but for the s d and f blocks, the rule works. I seriously doubt the Se powders are pure metallic bonds. I bet it is a small band gap semi-conductor like the rest of the semimetallics from some fraction of covalent bonds (espeically since adjacent elements are non-conductive). I've never heard of any metal that is monoclinic like Se. 99.99999% are BCC, FCC, or HCP. Crystal structure is directly related to properties, and metallic bonds are called so because there is no gap between the valence and conduction band. The electrons are free to drift around.

White powders are white because the tiny crystals scatter light. If we grew all the crystals to 1 big crystal, it would be transparent.

Just like if we grew millions of microscopic "ruby" crystals together, the part would look pinkish/red, and we would not be able to see through it. (some company actually makes armor tiles out of this material, which gets alot of frowns for the girly color). However, if we melted and grew the tiny crystals to 1 big crystal, it would be both transparent, red, and extremely valuable.

That means transparent stuff are a single pieces of large, big crystal? But should the bond be classified into metallic, covalent, ionic or others?

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