Inorganic chemistry/Atomic Structure

Each atom has Protons, Neutrons, and Electrons. Neutral atom, has equal amount of protons and electrons. Protons have positive charge "+", and electrons are negative "-", and thanks to the nature of neutrality, neutrons are uncharge particles. All protons and neutrons are called as nucleons of atom, and electrons surround around this nucleons ( we call these shells as orbitals, and they are most probable space that we can find electrons, more than 90%).

If we want to show the symbol of elements we need to know two definitions, atomic number, and mass number. The total mass of atom collect from the mass of electrons, protons, and neutrons. Since the mass of electron is very, very small, we can ignore it in total mass of atom. So if we want to measure the mass of atom, we can measure it with the amount of protons and neutrons that we have in atom. We call this number as mass number "A". Another useful definition is atomic number "Z", this number is the amount of protons that we have in atom.This information can be given simply in the form:

                                       A
                                        Fe
                                       Z