In nuclear physics and nuclear chemistry, nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits<span> into smaller parts (lighter </span>nuclei<span>). Hope this helps</span>
Counting atoms in a compound can be done by taking one element at a time and multiplying the subscript of the element and the number of molecules of the compounds. For example, H2O, there are two atoms of H adn 1 atom of oxygen.