When building an atom, pay close attention to the particles' electrical charges. Protons have a charge of +1. Electrons have a charge of -1. Neutrons are neutral, as its name implies. A stable ...

The nucleus is very small compared to the atom as a whole: as electrons are even smaller, most of an atom is empty space the diameter of a nucleus can be 100,000 times less than the diameter of an ...

Thus when an atom absorbs or gives off energy (as in ... number in their outer shells are less stable than those with "full" outer shells. Elements that have the same number of electrons in ...