The number of protons is what defines the element. Oxygen, for example, has eight protons. However, the number of neutrons in an atom can vary, leading to different forms of elements, called isotopes.

Both are made up of atoms which in turn are made up of protons, neutrons and electrons. But what makes oxygen different from carbon? It is the number of protons in the nucleus of an atom that is ...

Like ordinary water—H 2 0—each molecule of heavy water contains two hydrogen atoms and one oxygen atom ... As each uranium atom breaks apart, it shoots out neutrons that can go on to split ...

Image of the emission of 4 neutrons (blue spheres) from the exotic nucleus oxygen-28, which consists of 8 protons (red spheres) and 20 neutrons.

Different isotopes of elements have different numbers of neutrons. The most common isotope ... Water is made up of two hydrogen atoms and one oxygen atom, bonded together. In light water - by ...