radioisotope

The word 'radioisotope' is a modern scientific compound formed in the 20th century. Its first element, 'radio-', is derived from 'radioactive', itself from Latin radius (ray), alluding to the emission of energy rays. The second element, 'isotope', originates from Greek components meaning 'same place', coined to describe atoms occupying the same position on the periodic table. Thus, a radioisotope logically denotes an isotopic form of an element that is distinguished by its property of emitting radiation from its unstable nucleus.

Structure: radio (radiation) + isotope (same place) - radio: From Latin radius (ray, spoke of a wheel). In modern scientific use, it denotes radiation or radio waves. - isotope: From Greek isos (equal, same) + topos (place). It refers to forms of an element with the same atomic number (same place in the periodic table) but different atomic masses.