An atomic nucleus makes up a very small part of an overall atom, with a size from 1 to 10*10-15 meters, depending on the specific element. It is estimated that the nucleus of an atom only takes up 1/100,000 of the atom's volume, even though it contains almost all of its mass.
An atom's nucleus contains two types of particles: protons and neutrons. The protons have a positive charge, while the neutrons have no charge. This means that overall, an atom has a positive charge. However, there are orbitals around the nucleus that contain electrons, which have a negative charge. Depending on the number of electrons, the atom as a whole may have a negative, positive or neutral charge.