Emphasize that the atoms of all elements have the same basic structure. There is a central, dense core (nucleus) consisting of protons and neutrons surrounded by a field of electrons. The number of electrons will be equal to the number of protons. Each proton has a positive (+) charge; each electron has a negative (- ) charge; neutrons have no charge. (What is the charge of a atom if the number of electrons is equal to the number of protons?)
The number of protons, hence electrons, of an atom is key to its chemical nature. Thus, the atoms of each element have specific number of protons known as the element’s atomic number. (See the table above and note the atomic number of each element. Note how atomic numbers range from 1 (hydrogen with a single proton in each atom) to a somewhat over 100. Each atomic number is a different element.