Atoms

I've heard from many people that scientists have still not been able to determine what holds atoms together on the molecular level. I'm not sure if this is already a topic in discussion or not. If anyone knows any info on this topic let me know.

Thread moved here from the Proposed New Topics forum.

well, first off... molecules are larger than atoms. So your question really relates to sub-atomic physics, or perhapse even to quantum physics. A subject I know very little about.Just wanted to set you straight on the terminology

Your question is unclear to me. Are you asking how atoms are held together in molecules or are you asking how subatomic particles are held together in atoms?

The question is a bit confusing but I'll have a go. I'm sure others will as well.When you say at the molecular level I presume you mean what cause atoms to bind together into molecules. This is, as far as I know, very, very well understood.It is the electromagnetic force mediated by photons being exchanged that holds molecules together.The theory that describes this behavior is, I think, QED (quantum electrodynamics). This was developed orginally by R. Feynmann. It is a very precise theory. That is calculations done using it produce results that have been as accurate as the very best tests done. They are accurate to around 10 or so decimals.Can you tell us more about where you "heard"? One thing for sure is that lots of people say lots of things out of abject ignornance (me too, now and then ). The lesson might be not to believe everything you hear.

One of the most obvious signs of this happening is the following phrase: I heard somewhere that....

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Hate world.Revenge soon!

Ok, perhaps the question is in regard to atoms themselves separate from their incorporation into molecules.There are several parts to this, (warning now I'm really becoming uncertain of how firm all this is):1) Holding electrons around the nucleus.
This is also electromagnetic. The nucleus is positivly charged and electrons carry a negative charge.2) Holding protons and neutrons together in the nucleus.
Since neutrons carry no charge and protons are positive the nucleus has an electromagnetic force pushing it apart. This is where the strong nuclear force comes in. The neutrons and protons are bound together by the strong force. (IIRC, bosons are the exchanged particle). There have to be enough neutrons in the nucleus to "balance" the protons. Smaller nuclei have equal numbers of protons and neutrons (generally). As the atomic number goes up it starts to take more than an equal number of neutrons to hold it together. Eventually a nucleus can't be held together even with a significant excess of neutrons ( e.g., Uranium 238 has 92 protons and 146 neutrons). These elements are always radioactive.3) What holds the protons and neutrons together.Gluons hold them together. Gluons, I think, might have been detected in the very latest "atom smasher" experiments. Protons and Neutrons are made of "quarks" ( a term from James Joyce IIRC).That is probably as much detail as anyone could want. It is probably more than you wanted.What you 'heard' is correct in that we don't know everything. But it is very, very wrong given the amount that is known about this stuff.

I sincerely hope that the questions about atoms holding together aren't those raised by Jack Chick in his infamous tract "Big Daddy." The earnest young student in that masterpiece, totally unaware of all of 20th century atomic physics, says that Jesus holds atoms together. He must be a busy guy.There are a couple of forces with the unexciting names of the Strong Nuclear Force and the Weak Nuclear Force that are responsible for holding the nuclei of atoms together. They are very well understood indeed by folks that can handle the ugly mathematics that must be used to describe them. Forces like gravity and the electromagnetic force can be treated with nice, simple algebra; these two need tensor calculus or something even more horrific.

Ned wrote:
Note: talking about QED. And I'm just being a pedant here. Among others. Feynman's great rival, Julian Schwinger, and Sin-Itro Tomanaga shared the 1965 Nobel for their work on QED.Schwinger used a fairly complicated form of calc to get his answers (complicated because some of the infinities wouldn't go away if you did it the normal way) and Feynman created his Feynman Diagrams to get his identical answers in a graphical, easier to understand format. Tomonaga made his first breathrough in what became QED in 1942, but it didn't get much attention because the world was rather distracted at the time. He handled a slightly different part of QED theory (though I'm too ignorant to understand the distinction between his part and the part that Feynman and Schwinger did).Feynman was a showman who wrote a couple of popular non-science books for lay-people, Schwinger was a fairly reclusive academic who bored his own graduate students.This all came from a biography of Feynman (Genius by Gleick) so it's somewhat more pro-Feynman than I would like, but as all three were dead before I was 12 I obviously would have no first-hand knowledge of their personalities.ChrisThis message has been edited by cmanteuf, 03-31-2005 03:45 PM

I have Feynman's autograph on his "Character of Physical Law". He spoke here about 20 years ago.

Ned wrote: >>Jealous<<ChrisThis message has been edited by cmanteuf, 03-31-2005 03:49 PM

I have a question: Is it true that atoms are tasteless, colorless and odorless?

huh? I'd say "no".Taste or oder are a chemcial reaction. The substances that make up the compounds that are involved in that reaction are made of atoms. There is nothing else there so, in that sense, the atoms do taste or smell.

Nitrogen or oxygen molecules, at least - two atoms per molecule, in these cases, are indeed "tasteless, colorless and odorless," probably because our sensory apparati evolved immersed in them. We're built to ignore them. Same thing for atoms of the "noble gases" like argon and xenon - they are non-reactive with noses and taste buds, and give no response.Bromine molecules, though, when enough are present to impact our senses at all, look red, smell incredibly acrid, and probably taste even worse. Decent-sized chunks of sodium atoms, OTOH, are silvery and catch fire if the get up your nose or onto your tongue - they turn into sodium ions real quick in damp places. I'm sure the reaction tastes very bitter and bad.This message has been edited by Coragyps, 11-20-2004 02:37 PM

NosyNedOkay Ned How much do you want for it?LOL