The atomic radius of calcium (Ca) is approximately 197 picometers (pm). This value can vary slightly depending on the method used for measurement, but it generally falls within this range.
To explain further, the atomic radius refers to the size of an atom, typically measured from the nucleus to the outer boundary of the surrounding cloud of electrons. For calcium, which is found in group 2 of the periodic table, its atomic size is influenced by both its electron configuration and the number of electron shells.
Calcium has 20 electrons, arranged in two electrons in the first shell, eight in the second, and ten in the third. The presence of these electron shells contributes to the overall size of the atom. As we move down a group in the periodic table, atomic radius generally increases due to the addition of electron shells. Despite the increase, calcium’s atomic radius is smaller compared to larger alkaline earth metals like barium.