The material consists of “grains” called atoms. At the center of the atom are gathered particles called protons and neutrons. What differentiate them are their mass and their electrical charge: a proton is a little lighter and a positive charge, whereas a neutron is a slightly heavier and neutral charge (that is, Say it has no electrical charge!). Around this set called core, turn small elements very light and negatively charged: electrons.
It is the number of protons which makes it possible to say whether one is dealing with hydrogen, oxygen, calcium or iron. Indeed, the number of protons determines the chemical properties of the atom. On the other hand, for a given chemical element (hydrogen for example) the number of neutrons or electrons can vary. When the number of neutrons varies, it is called an isotope; when it is the number of electrons which varies, one speaks of ion.
An example is better than a long speech! Let us take calcium. In its core, there are 20 protons, no more, no less (otherwise it would not be calcium anymore!). But there may be 20, 22, 23, 24 or 26 neutrons. These five core configurations (20 protons + 20 neutrons OR 20 protons + 22 neutrons OR etc) are five isotopes of calcium.
Around the core of calcium should gravitate 20 electrons (as much as protons) so that there is electrical neutrality? But calcium easily loses 2 electrons during chemical reactions. With 18 electrons and 20 protons, it will be said to be the positive ion of calcium. If you want to know the difference between the more various things, then keep visiting Difference betweenz.