Atomic modeling with food particles
The most basic models of the atom are all in agreement, that within the nucleus, the densely packed center of an atom, resides the protons and the neutrons. The total number of these two types of particles together accounts for essentially all of the mass of an atom. The electrons "float" somewhere outside the nucleus in the electron cloud, with their exact location always changing. We tend to think of atoms that occur in nature and those that have made compounds, as neutral atoms. A neutral atom is one that has the same number of positively charged protons and negatively charged electrons. However, variations to those atoms exist in both the ion form and the isotope form. An ion is an atom with a net, overall ionic charge, either positive or negative, and that can only happen if the number of electrons does not equal the number of protons. Keep in mind however, that the number of protons serves as the "identification card" of the element, and is the same as the atomic number of that element. Isotopes are atoms of the same element with different masses, meaning that they must have a larger or smaller number of neutrons in the nucleus.