How to determine number of atoms and molecules in a formula?

Question

Given the formula H2O, there is one molecule with 2 atoms of H and 1 atom of O. But, how many atoms and molecules would be in a hypothetical formula 4R? Are there 4 molecules and 4 atoms of R? Or are there 0 molecules are 4 atoms of R? Can someone give me an explanation?

Answer 1

To go back to your H and O, there is only one more compound, hydrogen peroxide, H-O-O-H, Beyond that and water, there are no other compounds of H and O.

If you go on to C and H, there is an infinite number of molecules, and the sophomore organic course is occupied in writing them all down, naming them, and exploring their properties.

In your question 4R, take four carbon atoms. It turns out that there are two compounds of four carbon atoms, each of which is connected to hydrogen atoms. One is CH3CH2CH2CH3. The other has three carbons in a line, and a fourth sticking up in the middle : CH3CH(CH3) CH3. Beyond that, the number of compounds rises sharply exponentially as you increase the number of carbon atoms.