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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Rutherford on June 22, 2012, 02:41:15 PM

Title: Alpha Sn
Post by: Rutherford on June 22, 2012, 02:41:15 PM

How does α-alotropic modification crystal cell of stanium have 8 atoms?
http://imageshack.us/photo/my-images/577/20371450.png/
-8 on the slings are common for 8 cells: 8*1/8=1
-6 on the sides are common for 2 cells: 6*1/2=3
-6 inside (only common for one cell), so it should be 6+3+1=10, but is is 8, why?

Title: Re: Alpha Sn
Post by: Borek on June 22, 2012, 03:38:47 PM

8+6+6=20, but I can see only 18 atoms on your picture.

Title: Re: Alpha Sn
Post by: Rutherford on June 22, 2012, 04:21:30 PM

Edit: I never thought about counting them all at once, but yes there are 18 atoms so now, I could somehow see that there are only 4 atoms inside this cell that aren't shared with the other cells. Thanks for the corection, it helped me.
Isn't easy to distinguish in such a complex picture.