00:01
All right, so a hydrogen atom has one proton and one electron, and the proton is in the nucleus, electron is outside the nucleus, it has no neutrons, right? so, for part a, the fraction of mass that is in the nucleus, this fraction f will be equal to mass of a proton, that's the only thing in the nucleus, over the mass of proton plus the mass of the electron.
00:36
And so we know the mass of the proton is 1 .67 times 10 to the negative 27 kilograms, divided by, again, mass of the proton 1 .67 times 10 of the negative 27 kilograms plus mass of a electron, which is 9 .1 times 10 to the negative 31 kilograms.
01:03
And as you can see, this is four orders of magnitude, or at least three orders of magnitude smaller than the mass of a proton.
01:15
So proton mass dominates, and you can already see this will be a ratio very close to one.
01:19
If you put this in a calculator, you get .9945.
01:26
So 99 .9 .9 .95 % of the mass of a hydrogen atom lies in the nucleus, thanks to the proton.
01:36
Now, for part b, this fraction will be the volume of a volume v of a nucleus of the nucleus v .n to volume v of the whole atom va.
01:51
And assuming a spherical atom you have volume of a nucleus being 4 thirds pi times radius of the nucleus rn cubed volume of the atom is 4 thirds pi times radius of the atom r a cubed 4 thirds cancel so you're down to a ratio of the cubic ratio of the nucleus to the atoms radius cubed...