兄弟原子——同位素 19世紀末,人們发現了鈾具有天然放射性,能放出看不見的射綫,使照相底片感光。此后,人們便逐步认識到地球上的天然放射性元素原来多数都是由鈾、釭以及鋼鈾蛻变而来。这些原于是不稳定的;一面放出射綫,一面蛻变为其它放射性原子,直到形成非放射性原子, Brotherly Atoms - Isotopes At the end of the 19th century, people discovered that uranium had natural radioactivity and could emit invisible rays, making it sensitive to photographic negatives. Since then, people have gradually realized that most of the natural radioactive elements on the earth were originally transformed from uranium, plutonium, and steel uranium. The originals are then unstable; they emit rays and degenerate into other radioactive atoms until they form non-radioactive atoms.