同位素 ISOTOPE 一词,源出于希腊字 is-和 topos(place),意谓在元素周期表中占有相同位置而质量不同的原子。换言之,也就是原子序数相同而原子量不等,或者质子数相等而中子数不等的原子。同位素有两种,一种是放射性同位素或称不稳定同位素;另一种是非放射性同位素,即稳定同位素。迄今为止,已发现的稳定同位素有300多种,原子量一般小于40。 The term isotope ISOTOPE, derived from the Greek words is- and topos (place), means atoms that occupy the same place in the Periodic Table but differ in mass. In other words, they are atoms with the same atomic number but different atomic weights, or atoms with the same proton number and different numbers of neutrons. There are two isotopes, one is a radioactive isotope or unstable isotope; the other is a non-radioactive isotope, the stable isotope. To date, more than 300 stable isotopes have been found, with an atomic weight of less than 40.