Comment by saagarjha
7 years ago
Generally molecules are required to consist of at least two atoms bound bound together. For example, here's what Wikipedia defines them as:
> A molecule is an electrically neutral group of two or more atoms held together by chemical bonds.
Literally the next paragraph:
> In the kinetic theory of gases, the term molecule is often used for any gaseous particle regardless of its composition. According to this definition, noble gas atoms are considered molecules as they are monatomic molecules.[9]
This usage (considering "molecule" as a superset of "atom") is entirely confined to kinetic theory of gases AFAIK - ideal gas law, Boltzmann, etc - which treat gas particles as ping pong balls in Newtonian collision. Their composition is irrelevant, and it would be annoying always to write "molecule or atom".
The definition sounds very weird outside this context. You'd never hear a synthetic chemist talking like this!
It doesn't sound weird or objectionable to me to say "molecular helium" in casual speech, any more than any number of grammar errors I regularly commit... but if we're taking the time to get pedantic... no, it's not at all technically correct to say that helium is a molecule in the same way that a square is a rhombus.
Chemists ain't mathematicians. There's a useful distinction between things you can split and things you can't, and chemists (as opposed to thermo weenies) do in fact make it.