parent element

… T = log _e 2/λ ≒ 0.693/λ is called the half-life, and after this time the amount of a radioactive element will be half of what it was at first. If the amount of radioactive element (called the parent element) that was there at the beginning is N ₀ , the amount after a certain amount of time has passed is N , and the amount of stable elements (called daughter elements) that are produced by radioactive decay of the parent element is D ^* , then after T hours N will have decreased to N ₀ /2 and D ^* will become N ₀ /2. After another T hours N will be N ₀ /4 and D ^* will be (1 - N ₀ /4). …

*Some of the terminology explanations that mention "parent element" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…T＝log_e2/λ≒0.693/λを半減期といい，この時間たつと放射性元素の量は初めの1/2になる。初めにあった放射性元素(親元素parent elementと呼ぶ)の量をN₀，ある時間が経過した後の量をN，親元素の放射性崩壊によってできる安定な元素(娘元素daughter elementと呼ぶ)の量をD^*とすれば，T時間後にはNはN₀/2に減りD^*がN₀/2となる。さらにT時間後にはNはN₀/4,D^*は(1－N₀/4)となる。…

※「parent element」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報