It also tells us that chlorine has 18 neutrons (35 - 17) and, as the number of electrons and protons are equal in a neutral atom, chlorine also has 17 electrons. The relative mass of a nucleus is ...

Therefore, electrons cannot be arranged at random, but they must have fixed levels of energy within each type of atom. Bohr's 'solar system' model of the atom is the way that most people think ...

A simulation by US theoretical physicists has provided the first fully microscopic characterization of the moment an atom ...