I'm looking for the number for every possoble combination of Hydrogen isotopes and Oxygen isotopes, to find out how many "kinds" of water there are. I would love to do the math myself but i don't know how, so i ask you guys. Details below

One way to look at its is filling in different regions. If you have an object n and need to fill its first region you have n possibilities you have n1 combinations. Then for the second region you would have n possibilities for each region, so nn=n2. Then for the third region, nn*n=n3. So im sure you see the pattern that for an object n, with k regions you have nk ways to fill that region.

Using the example above in the water molecule there is only one oxygen region and there are only 16 isotopes to choose from so 161. However there are two hydrogen regions each can be filled by one of 7 different isotopes thus there are 77 or 72 combinations. Thus in total there are 1672 = 784 combinations.

Sorry about the formatting im on mobile.

/r/mathematics Thread