The number of protons is what defines the element, i.e. an atom with six protons in its nucleus will always be carbon, and uranium will always have 92 protons. The total number of particles in the ...

After tracing many particles and examining the patterns, Rutherford deduced that the atom must have nearly all its mass, and positive charge, in a central nucleus about 10,000 times smaller than ...

The electrons in an atom tend to occupy distinct shells. What about particles in the nucleus? The "magic numbers" of the isotope chart suggest that they also have a shell arrangement ...