Prehistoric materials are dated by measuring the atomically unstable isotope carbon 14. 史前物质的年代是通过测量原子上不稳定的同位素碳14来确定的。
Elements grouped in the same area of the periodic table are related atomically and chemically. 分布在元素周期表同一区域的元素在原子上和化学上是相互关联的。
See: atomic