Question about lattice points?

Question

Do diagrams that show unit cells with atom/s located at each lattice point actually represent the "centre" of atom/s? When we see pictures of unit cells the lattice points are spread apart and you get 3-D box like constructions. As there are no spaces between atoms in unit cells I assume that we are actually looking at atom centres for each lattice point?

Answer 1

That is correct. In the ball-and-stick models of atoms typically drawn in books, each ball represents the center of an atom. In a lattice, each vertex of the lattice is the center of an atom. Here's a picture of the ball-and-stick model:

http://en.wikipedia.org/wiki/Image:Jmol1.png

If you use the more realistic space-filling model, molecules look more like a bunch of balls that have been mashed together. Here's a picture of the space-filling model:

http://en.wikipedia.org/wiki/Image:FormicAcid.pdb.png