1.In meson-exchange model description of nuclear force, themost important one is the pseudoscalar meson pions, which provide the longest range force between to nucleons.
12.Specifically the mass of the nucleus, exactly 15.99 atomic mass units, is lower than the mass of its individual nucleons put together, in this case 16.13 amu's.
14.The amount of energy required to break up a nucleus into its component particles gets larger as the atomic number increases, with iron having one of the highest binding energies per nucleon.