Hello there!
To determine the fraction of the hydrogen atom's mass that is in the nucleus, we have to keep in mind that
a Hydrogen atom has 1 proton and 1 electron.
Protons are in the nucleus while electrons are in electron shells surrounding the nucleus.
The mass of the nucleus will be equal to the mass of 1 proton and we can express the fraction as follows:

So, the fraction of the hydrogen atom's mass that is in the nucleus is
0,9995. That means that almost all the mass of this atom is at the nucleus.
Have a nice day!
Answer:
Joule - J
Explanation:
As energy is defined via work, the SI unit of energy is the same as the unit of work – the joule (J).
No its a example of heterogeneous mixture
First of all, it is a nucleic acid, not nuclear acid.
Examples are DNA and RNA( Deoxyribonucleic Acid and Ribonucleic Acid)