Editing Specific activity (section)

===Other calculations===
{{cleanup merge|Becquerel|21=section|date=July 2023}}

For a given mass <math>m</math> (in grams) of an isotope with [[atomic mass]] <math>m_\text{a}</math> (in g/mol) and a [[half-life]] of <math>t_{1/2}</math> (in s), the radioactivity can be calculated using:

:<math>A_\text{Bq} = \frac{m} {m_\text{a}} N_\text{A} \frac{\ln 2} {t_{1/2}}</math>

With <math>N_\text{A}</math> = {{val|6.02214076|e=23|u=mol-1}}, the [[Avogadro constant]].

Since <math>m/m_\text{a}</math> is the number of moles (<math>n</math>), the amount of radioactivity <math>A</math> can be calculated by:

:<math>A_\text{Bq} = nN_\text{A} \frac{\ln 2} {t_{1/2}}</math>

For instance, on average each gram of [[potassium]] contains 117&nbsp;micrograms of [[Potassium-40|<sup>40</sup>K]] (all other naturally occurring isotopes are stable) that has a <math>t_{1/2}</math> of {{val|1.277|e=9|u=years}} = {{val|4.030|e=16|u=s}},<ref>{{cite web|url=http://nucleardata.nuclear.lu.se/toi/nuclide.asp?iZA=190040 |title=Table of Isotopes decay data |publisher=[[Lund University]] |date=1990-06-01 |access-date=2014-01-12}}</ref> and has an atomic mass of 39.964&nbsp;g/mol,<ref>{{cite web|url=http://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=&ascii=html&isotype=some |title=Atomic Weights and Isotopic Compositions for All Elements |publisher=[[NIST]] |access-date=2014-01-12}}</ref> so the amount of radioactivity associated with a gram of potassium is 30&nbsp;Bq.