Here's how to determine the number of valence electrons in a calcium ion (Ca²⁺):

* Neutral Calcium: Calcium (Ca) is in group 2 of the periodic table, meaning it has 2 valence electrons.

* Ion Formation: Calcium loses two electrons to form a +2 ion (Ca²⁺). This means it loses its valence electrons.

* Valence Electrons in the Ion: Therefore, a calcium ion (Ca²⁺) has zero valence electrons.