Discussion Forum (Archived)
Guest
My background is also in science, and the definition I've always used for molecule is far simpler, and matches what the online dictionary says:
A group of two or more atoms linked together by sharing electrons in a chemical bond. Molecules are the fundamental components of chemical compounds and are the smallest part of a compound that can participate in a chemical reaction.
So it doesn't make any difference whether the bond is ionic or covalent … only that electrons are being shared. I would also agree, on those grounds, that DNA meets the definition of molecule. Likewise NaCl, even though the valence electrons in crystal tend to wander all about. In fact, that's why metals (in their crystalline form) tend to be such good conductors of heat and electricity.
Same with nucleotide. The definition here is:
Any of a group of organic compounds composed of a nucleoside linked to a phosphate group. Nucleotides are the basic building blocks of nucleic acids.
And the nucleoside and phosphate group are again held together by shared electrons.
We're getting out of language and into science, here, but what I learned in school is that ionic bonds DON'T share electrons. In NaCl, for example, the "extra" sodium electron is not shared between them (as it is between two hydrogen atoms, for example, or in a molecule of water), but is simply stolen by the chlorine atom; after that the two atoms are "ions" and held together by electromagnetic attraction, positive to negative. Strictly speaking, then, salt would not be a molecule. But even if that definition is technically correct, I would not be surprised to learn that most chemists still speak of "a molecule of salt" in casual conversation.
You're right, Bob, about ionic bonds being more "stealing" than "sharing" of electrons. And you're also right that this thread is wandering away from language and more toward chemistry. That being said ... (hey, that was another thread) ... the electron(s) in an ionic bond can be found around either atom with differing probabilities. It's probably online somewhere, but I'm guessing the electrons have a 90%+ probability of being found around the chlorine atom in NaCl, and maybe 10% around the sodium atom. There are no absolutes in quantum mechanics.
I look at the title of this thread, and feel guilty about causing this wandering. 
LOL; I was constructing an argument in my head yesterday morning, and caught myself saying "That said...", which reminded me of the recent thread. This forum is apparently having 'way too much influence on my thought life.
Only 90% and 10%, eh? So what I remembered from school was too simple, and by that measure I should think of salt as molecular after all; even though ionic attraction plays a much greater part, the electron bond still exists and has some influence.
I wonder how they know where the electron is?
I wonder why some declarative statements require an interrogative instead of a period?
Martha Barnette
Grant Barrett
Grant Barrett
2 Guest(s)