: Atoms can lose or gain electrons to become ions (charged particles) or vary their number of neutrons to become isotopes of the same element.
: Positively charged particles located in the center of the atom (the nucleus). The number of protons determines the identity of the element.
: Most of an atom's volume is actually empty space. If an atom were expanded to the size of a football stadium, the nucleus would be the size of a marble in the center, and the electrons would be like tiny gnats buzzing around the highest seats.
