Calcium ion
Charge: 2+ · Type: Cation · Molar mass: 40.078 g/mol
Made of: calcium
How it forms
Calcium has two valence electrons. Losing both gives Ca2+ the electron arrangement of argon. Because removing two electrons costs more energy than removing one, calcium ionizes fully mainly in energetic reactions such as reactions with acids or halogens.
Naming note
Ca2+ is the calcium ion. The Roman numeral is not needed in the name because calcium has only one common ion charge.
Examples in compounds
Calcium carbonate
Calcium chloride
Calcium hydroxide