Complete Lapidary

Complete Lapidary
Carbon atoms on surface of diamond unsaturated?

In a fit of largesse I bought four sets of organic chemistry model pieces (molymod), confident that I had overcome the only thing that prevented me from modeling the structures of diamond and graphite for my kids’ class at the local lapidary society–i.e., not enough four-hole carbon atoms.

Sadly, my ignorance seems to be a barrier, too!

After four hours I proudly presented my completed diamond model to my daughter, who said, “Um, Mom, shouldn’t it be an octahedron?” “It IS an octahedron!” I protested, until I counted the sides. Nope, I’d somehow managed to construct a TETRAHEDRON. I had to start over (daughter’s hands aren’t strong enough to snap the pieces together, or I’d have her do it).

I now have an octahedron…but I won’t show it to my kids for fear that they’ll ask me, “Why do all the carbons on the outside of the diamond still have one hole left over?” Because I dunno.

So, are those surface atoms double-bonded, or bonded to junk on the surface, or ?

searching the internet I found something on diamond like carbon substances and how they are produced through the randomization of sp3 hybrids and sp2′s, this randomization keeps the cubical carbon bonds from “springing” back into there original sp2 configuration. So in these diamond like substances its the packing in of space which holds some of the cubical shape.

sp3 orbitals = cubical formation
sp2 = hexagonal

so basically the sp2 takes up space holding in the sp3 carbons in shape

in a real diamond this can be applied to show that the outer most carbons are in the sp2 configuration locking in the sp3 carbons on the inside

exactly how you can model this, i don’t know – this is only my guess however, but it makes sense

7. Vladimir Nabokov, Lolita (cont.)