Here's why:
* Isotopes: Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means they have the same atomic number but different atomic masses.
* Calcium: Calcium has an atomic number of 20, meaning every calcium atom has 20 protons.
* Calcium-40: Calcium-40 has 20 protons and 20 neutrons, giving it an atomic mass of 40.
While there are other calcium isotopes (like Calcium-42, Calcium-43, Calcium-44, Calcium-46, and Calcium-48), Calcium-40 makes up about 96.941% of naturally occurring calcium, making it the most abundant and stable isotope.
