[appleseed]

are compounds and molecules the same thing?
for example H2O is a compund of hydrogen and oxygen
. i can also say that H2O is a molecule of hydrogen and oxygen

[Yggdrasil]

Not all molecules are compounds.  For example, O₂ is a molecule (consists of two or more atoms covalently bound together) but not a compound (a substance consisting of two or more elements).

Not all compounds are molecules.  For example, NaCl is a compound, but it is not a molecule (Na and Cl are bound by ionic bounds and form a crystal lattice, not a discrete molecule).

[appleseed]

Thankyou Yggdrasil for the reply, I think i have a better idea of the difference now.
But i dont understand how O2 is not a compound.
So O2 is a molecule because it is covalently joined together.
But my idea is that O2 consits of two oxygen atoms, and an atom is an element, that are joined together.
So O2 consits of two element atoms that have joined to gether so its a compound?

im very confused because a molecule is a substance covalently joined togerther, in that case H2O is a molecule and NOT a compound because it is covalently joined?

i have searched on some sites and some of the definitions are very different!
some say that a compound is when two or more different atoms joind together
and a molecule is when two atoms join together
and they also say that
All compounds are molecules, but not all molecules are compounds

confusing eh?

[macman104]

Thankyou Yggdrasil for the reply, I think i have a better idea of the difference now.
But i dont understand how O2 is not a compound.
So O2 is a molecule because it is covalently joined together.
But my idea is that O2 consits of two oxygen atoms, and an atom is an element, that are joined together.
So O2 consits of two element atoms that have joined to gether so its a compound?

A compound is two or more elements not atoms.

im very confused because a molecule is a substance covalently joined togerther, in that case H2O is a molecule and NOT a compound because it is covalently joined?

Read above a compound has two or more elements.  A molecule is a covalently bonded network of atoms, regardless of whether they have only 1 type of element or more.

BTW, I'm simply going off of what Yggdrasil used a definition to help explain.

[appleseed]

Ok let me get this straight.
all elements are made of atoms, its just that an element is made of atoms that are all the same. a single atom = an element Right? so atoms would be under the element category. eg water contains hydrogen and oxygen elements joined together, Right? so why is it not a molecule
then I dont understand what the difference would be if compounds are of covalently joined atoms or elements. and from the example of NaCl that is not a molecule because its ionic bonds, does this mean that all compounds are ionically joined together?

if a compound is a substance consisting of two or more elements. does this mean that they the two elements have to be different? because no same elements will join together ionically.

to sum up my questions
*The idea that all compounds are molecules is wrong, Right???
*whats the difference between atoms and elements in relation to this?
*compounds are ionically joined together and molecules are covalently joined together. Right???
*compounds contain two or more different atoms/elemts joined together?
  CAN YOU GIVE ME EXAMPLES PLEASE
Thankyou!!

[Yggdrasil]

to sum up my questions
*The idea that all compounds are molecules is wrong, Right???

Correct

*whats the difference between atoms and elements in relation to this?

Let me clarify my definitions more.

A molecule is a substance consisting of two or more atoms covalently bound together.

A compound is a substance consisting of two or more different types of atoms.

O₂ is not a compound because it consists of only one type of atom (oxygen atoms)

H₂O is a compound because it consists of two different types of atoms (hydrogen and oxygen atoms)

*compounds are ionically joined together and molecules are covalently joined together. Right???

Wrong.  See the H₂O example.

*compounds contain two or more different atoms/elemts joined together?

Yes.

[rahul2ghosh]

Very well explained by Yggdrasil.. 

However, just to add few things...

Molecules are subsets of both Elements and Compounds. As O₂ is molecule of an Element and H₂O is Molecule of Compound.

Now Compounds are both Ionic and Covalent in Nature. Ionic Compounds in Solid State exist as Crystals and thus Molecule has no meaning here. However, for e.g, when NaCl is vaporised, its Vapor consists of NaCl molecules. Here also you can see that NaCl is molecule only because it has atoms from two different elements. Though in this case, we have charged atoms in the form of Cation (Na⁺) and Anion (Cl^-).

In case of Covalent Compounds too we have examples like Polymers where a molecule has no meaning.

Rahul