Atoms

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.

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

Correct, if you'll let me replace "detectable" with "able to be imaged." The gas in a neon light, for instance, emits photons at one per atom that we can see, so the atoms are "detectable" at our eyes' wavelengths.
There are "pictures" of atoms lined up in crystals and the like - these are made using atomic force microscopy or AFM. I know almost nothing about how it works, though http://stm2.nrl.navy.mil/how-afm/how-afm.html helped somewhat. I haven't Googled up anything yet that has both explanations and some good pictures, though. No, it's not that simple. Your cannonball analogy still applies, for one thing. And secondly, a piece of silver or copper looks the way it does mostly because of the "sea" of electrons that surround the individual atoms in the crystals. I read a little more detail on this 30 years ago, but that detail is gone, along with its source, from my brain. Now in the case of a colored gas or liquid - chlorine or bromine - I suspect that the color is intrinsic to the molecules - sets of just two atoms in these cases. These actually absorb certain wavelengths of light, leaving a color we can sense.

Electrical forces - specifically the electron clouds around atoms, that are either shared between atoms or donated by one atom to another. It's about two chapters' worth of a beginning chemistry book - look for "ionic bonds", "covalent bonds", and "van der Walls bonds (or forces)".At 2000 degrees Celsius, all your molecules will indeed float off. Stay out of places that hot.

No, red-shifted light would actually appear redder than unshifted, as long as you weren't shifting ultraviolet light up into the visible .... There aren't any deep-sky objects that are redshifted significanly that are bright enough to see any color in at all with the naked eye, and very possibly not even with a BIG telescope in front of your eye. If you had a sodium-vapor streetlight on a fast rocket (sodium-vapor because it emits almost all its light at one wavelength) it would appear red instead of yellow if it was moving away from you at, say, 20% of the speed of light, and pure blue if it was moving toward you at some similar speed. Only in that the nucleus determines, through its total charge, how many electrons you have and the energy levels they can occupy. Electrons hopping between levels do all the "doing" that has to do with light in the energy range that we can see. Nuclei give of x-rays when they swap energy levels. There's no difference between them - light has no memory.

I've read about quark stars too - apparently it's still a hypothetical. I don't know just how you could distinguish a quark star from a neutron star anyway. I'm not going to volunteer to go scoop up a sample.

0.18 nm is 1.8 Angstroms. That would have been easily measured by the spectroscopists back before 1900. Perhaps a bit close for something like my Spec20, but not terribly difficult.This message has been edited by Coragyps, 11-18-2005 04:16 PM

Just a regular ol' prism spectroscope with sufficient focal length would be fine. They're probably more an astronomical tool than a chemical one, but were used a lot in the late 1800's before we had all this electronics to do the heavy lifting for us. The yellow emission lines of sodium are only 7 Angstroms apart, IIRC, and they were well known to be a doublet back in Bunsen and Kirchoff's day.Atomic emission and absorption spectrometers nowadays, I think, use filters to isolate wavelengths they aren't using, and choose the lines they measure to avoid as much interference as possible. They don't need great resolution, in other words. And, of course, hydrogen and deuterium differ more in properties than any other pair around due to the mass difference being a factor of 2.