Question

what decide nuclear hydrogen atom size?

Answer 1

size of an atom depends on how far away its outermost (valence) electrons are from the nucleus.

Answer 2

For the nucleus size that you ask, I ll consider the hydrogen protium isotope here. (not just because its simpler but to be honest my knowledge is limited too, i am just a high-school graduate right now). So protium--> 1 proton. that's it. no other repulsion from any other proton. nor any attraction with any other nucleon due to nuclear forces. so it's basically just the radius of a proton that counts. and its of the order 1.75 fermi meters generally. whereas in deuterium and tritium things are pretty much similar to the multi-nucleon species:
So, in multi-nucleon species, the size of the nucleus is a combined factor of repulsion between the protons, plus the inter-nucleon attractive force (nuclear forces bet ween both protons and the neutrons) The radius of the nucleus is then whatever is optimum for its potential energy, or stability. ofcourse the nuclear forces are much greater than magnitude.

Plus apart from that, inside the nucleus exist orbital pattern similar to the atomic orbital, with orbits, energy shells assigned to nucleons with spin factors there as well. . So, as far as the structure of the nucleus is concerned, it's pretty complex too.
(and let me tell you nothing is yet ascertained about how exactly he forces originate, and high level research is still on. there is the quark theory, but nothing is ascertained yet as it has not been possible to "image" a nucleus in real time, like electrons.

Answer 3

LOL. :D

Answer 4

thank
shruti.