Does an atom even have a physical shape? If so, what is it?
Is it even meaningful to talk about the shape of an atom, with its probability clouds?
One might reflexively say it’s spherical, but I fear that this is overly simplistic.
All models we have for the atom are exactly that; models. We can say that, in certain cases, an atom looks like this. Then in other cases looks like that. Both models are true, and yet at the same time, inaccurate. But we need to refer to these models in order for our macro-world bound brains to get a grasp of the quantum level. Without these models the physical aspects of the quantum level are so mind-boggling remote from anything we can relate to that they would be impossible to comprehend.
So, yes, an atom is spherical. But, no, not really. Ultimately the most accurate answer is that its shape is undeterminable, but that’s not much help. So we have to start introducing concepts such as probability and electron clouds. But they’re just more models that are probably not very accurate either.
Simple low MW atoms have a spherical shape where 95-99% of the electrons hang out, but higher order atoms have electrons in various 3 dimensional orbitals. The atom may have different shapes in molecules that it forms. carbons form molecules where the attached atoms are tetrahedral around it, as well as other shapes. Depends. Molecules have definite 3d shapes.
If you can open the Acrobat files, pictures of molecules in 3D
http://www.ch.ic.ac.uk/local/organic/mod/
Here are several different ways of picturing atoms.
The one that has
www.cc.gatech.edu/scivis/ research/atom/atom.gif
emphasizes that many atoms stack like balls. The radius of the ball is called the Van Der Vaal radius of that atom
try www.cc.gatech.edu/scivis/ research/atom/atom.gif or just cut and paste from my previous post
Hmm, third time or go to knitz link
they are not spheres, more like flattened spheres here.
Futile Gesture wrote:
In the vein of Futile Gesture’s post, I’m not sure that shape is a term that can be easily applied to atoms. Remembering back those many, many years to organic chemstry it seems to me that electrons clouds (which make up over 99.9% of the volume of an atom) become more and more unpredictable the further they are from the nucleus.
If you could “see” an atom what you would see would be the ever changing pattern of the outer shell. I’m guessing that ‘shape’ is not a good atom descriptor.
Futile Gesture: Edmonten (SP?) or Thorne couldn’t put it much clearer than you did.
Thanks.
You ever seen a Koosh ball? Well… atoms are just like that.
The shape of an atom is the shape of its outer orbitals. Here’s an article from Nature about this (9/2/1999 p21)
Non-spherical charge distribution of atoms’ electrons observed
I think that a single atom alone in space has a fuzzy wavelike orientation, and only when it’s bonded with other atoms does it’s orientation and shape become “real.”
It’s like a Pringle. Oh wait, nevermind
We poor mortals have minds that don’t deal very well with entities that are “vague.” We want hard and fast rules, yes-or-no answers, and sharp-edged objects.
Atoms refuse to comply.
Maybe this is a help, though. Think of a roundish clump of foliage. If you think about the individual leaves, the clump has no “shape” that can be summarized accurate in any common word. But you can consider it in “general” terms, and say that it is more like spherical than it is like anything else.
And so it goes.
Look for info on the shape of the s,p,d, etc. orbitals and you’ll discover that atoms have a distinct shape. Some have two lobes or “petals”, others are tetrahedrons, others look like a donut with two blobs extending axially out of the holes.
Oxygen atoms can be seen as tetrahedrons. That’s why hydrogens bond at an angle rather than a straight line in H2O. The hydrogens bond to two of oxygen’s four “vertices” or orbital lobes, and the other two lobes stick out invisibly from the oxygen atom (they weakly bond to other hydrogens during the liquid or solid phase.)