1)name and describe the four forces that are at work within

1)name and describe the four forces that are at work within the nucleus of an atom.
residual strong force(binding force), electromagnetic forces(van der Waals forces),gravitational force
2)the metal thallium occurs naturally as 30% thallium-203 and 70% thallium-205. calculate the atomic mass of thallium.
204.4
3)why is gravitational force in the nucleus so small?
Because the nucleus itself is very small, and F=mg, gravitational force is proportional to the mass.
4)could a nucleus of more than one proton but no neutrons exist? explain.
No.
An atom with more than one proton with the smallest atomic number is Helium. Helium has isotopes 3-He and 4-He, it is only stable when there are at least one neutron, hence a nucleus of more than one proton but no neutrons do not exist. The neutrons also balance out the forces within the neucleus. With only protons, the repulsion would be too strong for the binding force to balance.
呵呵,我在国外学习,去年才学的这些.现在都已经忘了不少了,哈哈哈哈.