How do scientists determine structures and forumulas of molecules such as sugar?.......?

Question

I always read in the books about really long molecular forumulas about amino acids and carbohydrates but i wonder, since we can't see atoms at all, how do scientists determine the amount and they types of atoms as well as the type and size of the bonds?

Answer 1

One way is by growing a big, pure crystal of the material. Since all the molecules are the same, and the crystal is pure, then all the molecules must fit together a certain way to form the shape of the 'ideal' crystal.

X-ray crystallography, which the previous answerer referred to, is when they shine a thin beam of x-rays through the crystal, to see how they are diffracted. This shows how the crystal is constructed inside.

In addition to this, if the molecules are large enough, an electron microscope can sometimes see the layers of molecules on the outside of a crystal, or the inner layers if it is split open.

By using techniques like this, scientist can build up a mental concept of what shape and size the basic units of the crystal must be, the molecules. Then they can make little stick-and-ball shapes that represent the molecules and build up large structures (representing very tiny crystals.) If their predictions are correct, the large shape they build up should resemble the actual crystals, with the same angles and the same shape planes, etc.

19 NOV 06, 1756 hrs, GMT.

Answer 2

nuclear magnetic resonance spectroscopy (NMR), infra red (IR) spec, mass spectrometry (MS), x-ray crystallography (XRC)

all v complex technical things, too difficult to explain, but look these up in wikipedia