Half-life of Radioactive Substances

A calculator for the half-life, the amount of a substance at the beginning, the time passed and the amount remaining at that time. Original and resultung amount have the same value (e.g. Kilogramms, Milligramms, %, etc.), as well as half-life and time passed (one unit, e.g. s, min, h, d, a, etc). Please insert three values, the fourth will be calculated. Any of the four values ​​can be left blank.

Example: the very rare but naturally occurring carbon 14 has a half-life of 5730 years. This isotope is used for radiocarbon dating, which can be used to determine the age of organic substances. The proportion of ¹⁴C that a living being has at the time of death is known because this isotope is newly produced in the atmosphere at a roughly constant rate, is therefore present in a fairly constant amount and is absorbed through metabolism. For every trillion carbon nuclei there are 1.25 nuclei of this isotope. If you start from an initial amount of 100, regardless of whether that is nanograms or you see it as a percentage, and 80 (nanograms or percent, same information as before) are still present, then about 1865 years have passed.
This method can be used for periods between about 300 and 60,000 years, although it becomes less accurate the closer you get to the upper or lower limit.

It is impossible to say when a single atom of a radioactive isotope will decay. However, we usually have a very large number of atoms. For example, a gram of carbon contains 50 sextillion atoms, see the atoms per mass calculator. Of this large number, it is possible to say very precisely after what time half of the atoms have decayed, but not which ones these are. After one half-life, one half (1/2) has decayed, after two half-lives it is 3/4, after three 7/8, after four 15/16 and so on, until after about ten half-lives the number is too small to make this calculation possible.