Calcium is a soft gray metal best known for being an essential element for living organisms, including humans. It is also a chemical element and is represented by the symbol Ca and the atomic number 20. Calcium is the fifth most common element on the planet by mass and it is also the fifth most common dissolved element in seawater by mass. Calcium is never found in its free form on Earth, but is found in many minerals from which it can be extracted. In fact, there are well over 200 minerals that contain calcium. All calcium found on the planet is made up of 7 separate isotopes, but many more isotopes of calcium have been identified.
How many isotopes does calcium have?
There are five stable isotopes of calcium; 40C, 42C, 43C, 44C and 46C. In addition to this there this one isotope, 48C, that has a half-life that is so long that it is considered to be stable for practical purposes (40C and 46C may also be theoretically unstable). 41C is another long lived isotope with a half-life of about 102,000 years. These seven isotopes make up all of the natural calcium found on the planet. Most of this is 40C, which makes up almost 97% of all calcium on Earth. 44C makes up 2%, 42C accounts for 0.6%, 43C is 0.01% and the others are found in trace amounts only.
In addition to these seven elements there are seventeen other unstable elements of calcium (that makes 24 in total). All of these have half-lives of less than 164 days and many of them have half-lives under one minute. The most stable of the artificial isotopes of calcium is 45C , with a half life of 163 days. The most unstable isotope of calcium is 34C with a half-life of just 35 nanoseconds.