The Atomic Mass of Calcium, Isotopes, and Atomic Weight

The atomic mass of calcium, isotopes, and atomic weight

The relative atomic mass of Calcium is 40.078 u (unified atomic mass unit) or Da (Dalton). 

Sometimes we confuse atomic mass and atomic weight. Atomic mass is the mass of an atom, whereas atomic weight - or relative atomic mass- is the weighted average of the naturally occurring isotopes.

The next table shows the atomic mass of each isotope of Calcium and the percentage of his isotopic composition.


Atomic mass (Da)

Isotopic abundance (amount fraction)


39.962 5909(2)

96.941% (156)


41.958 618(1)

0.647% (23)


42.958 766(2)

0.135% (10)


43.955 482(2)

2.086% (110)


45.953 69(2)

0.004% (3)


47.952 5229(6)

0.187% (21)

Source CIAAW

What Is Calcium?

Calcium (Ca) is a chemical element of the periodic table with the atomic number 20.

The simple substance calcium is a soft, reactive alkaline earth metal of a silvery-white color. G. Davy was the first scientist to obtain its pure form in 1808.

Due to its high chemical activity, we can not find free calcium in nature. However, we can obtain free metallic calcium by electrolysis of a melt.

Calcium is the 5th most abundant element on Earth after oxygen, silicon, aluminum, and iron). It is also plentiful in seawater, where the content is about 400 mg/l. The 3.38% of the mass of the earth's crust is Calcium.

This chemical element is a typical alkaline earth metal. It has a high activity, although other alkaline metals are more active.

We can find it associated with carbon dioxide, oxygen, and moisture in the air.

What Is the Atomic Mass of Calcium Carbonate?

The molar mass of calcium carbonate is 100.0869 g/mol.

Calcium carbonate is a particular chemical compound used in many uses, such as medicine. We need calcium to maintain healthy muscles, bones, the heart, and the nervous system. Therefore, calcium carbonate is a dietary supplement used when the amount of calcium consumed through the diet is not enough. However, consumed in excess can be hazardous and cause digestive issues and hypercalcemia.

The formula of the Calcium carbonate is CaCO3.


Published: August 24, 2021
Last review: August 24, 2021