I know that one hydrogen atom is one angstrom, but how big would it be with two oxygen atoms attached to it? There's a question on my textbook's website about it.

Water is one OXYGEN with two Hydrogens attached.- Thus H2O. The 2 coming after the H means there are 2 of them not the oxygen.

 

This site: http://www.lsbu.ac.uk/water/molecule.html - goes on about the size and dimentions of the water molecule from what I could tell.

QUOTE: "Water molecules are tiny and V-shaped with molecular formula H2O and molecular diameter about 2.75 Å."

 

Type "water bond length" into google and have a read around.

bear in mind that any sizes given to atoms or molecules are somewhat arbitrary, since the positions of the electrons can only be determined probabilistically, meaning that atoms and molecules could be considered to have infinite size, but just massively higher electron density at the centres.

In solids you can measure the size of the molecules to great accuracy by Xray diffraction. If all the molecules are the same then you can say that their size is the same as the separation between one and the next in the lattice.

If you look here

http://www.lsbu.ac.uk/water/ice1h.html

you can see the dimensions of the lattice of water molecules in ice crystals measured to 5 digits.

On a side note, here, there are also some beautiful images of gold atoms reconstructed from a scanning tunnelling electron microscope. So atomic surfaces that are smooth enough can be 'seen.' Here's the image:

 

Edited July 12, 200817 yr by jimmydasaint
Forgot a sentence