An element's atomic number defines it. An element with 17 protons will always be chlorine. However an element's mass numbers can vary, which means that it can have different numbers of neutrons. So ...

A supercomputer has calculated the number of isotopes allowed by the laws of physics. Physicists used a quantum approach known as density functional theory, applying it independently to six leading ...

Mirror magic: The "cores" of the exotic nuclei oxygen-22 and silicon-22 both resemble that of oxygen-16, with eight protons and eight neutrons. The neutron-rich oxygen isotope contains an additional ...

Part of Physics (Single Science) Unit 1: Atomic and nuclear physics Protons and neutrons are the heaviest particles in an atom and as a result they make up most of its mass. The mass of electrons is ...