[realdeal012]

I'm a Freshman in undergrad and I'm realllly having understanding very basic concepts of chemistry. I think I understand atoms and elements and compounds. From what I have learned, everything is composed of atoms. Different atoms are different elements. When you change the number of protons in an atom you change the element. A compound is 2 or more elements and has  a new set of properties. Here is where I get a headache: molecules. I know I should understand what a molecule is but I just don't. So I guess my questions are these:

1) what is a molecule? I have read definitions of a molecule everywhere ranging from the Internet to my chemistry book and they all give different answers. I have read something about when nonmetals bond???

2) what are molecules of an element and molecules of a compound? Are they the same thing?

3) are all atoms elements? I guess what I'm asking is: is a certain element a single specific atom? Or can an element be several atoms bound together?

Like I said i know this is elementary stuff but I honestly am having a hard time with it. Thanks in advance.

[curiouscat]

3) are all atoms elements?

Yes. Barring some semantic issues.

Or can an element be several atoms bound together?

No. Though some people do refer to O2 / N2 etc. as elements but strictly O and N are the elements.

[Hunter2]

what are molecules of an element and molecules of a compound? Are they the same thing?

Molecules are compounds of more then 1 atom.

Elements like already mentioned  can exists as molecules like all the gas elements H₂, N₂,O₂, halogens and some others like S₈, P₄, etc.

Compounds contain different elements.

From molecules is spoken also if you non metal compounds, like water carbon dioxide, etc. If you have for example sodium chloride NaCl we don't talk about a molecule even it is. Its a salt compound.

[Dan]

Realdeal012, definitions for these terms are very easy to get hold of - look them up, e.g.

http://en.wikipedia.org/wiki/Chemical_element
http://en.wikipedia.org/wiki/Molecule
http://en.wikipedia.org/wiki/Chemical_compound

Where, specifically, is the confusion?

[realdeal012]

I get confused at molecules. I understand atoms and elements. My problem with molecules is that there are too many definitions. My teacher said something about a molecule is when non metals bond. I have seen definitions where people say molecules are when atoms of the same element bond. And others' definitions of molecules sound almost exactly like compounds, but i know there is a difference. I just don't know exactly what the difference is. Molecules sound the same as compounds to me.

[Borek]

Molecule is anything that is made of several atoms, no matter what kind of atoms these are. Compound is anything made of several different elements. So you can have a molecule that is not a compound - like O₂.

[realdeal012]

Okay that makes more sense. Thanks

[Dan]

I drew a Venn diagram of this a while back, here it is:

http://www.chemicalforums.com/index.php?topic=60333.msg215945#msg215945