Answer: 4s orbital contains the electron that calcium loses to form an ion
Step-by-step explanation:
Electronic configuration represents the total number of electrons that a neutral element contains. The electrons are filled according to Afbau's rule in order of increasing energies.
Calcium with atomic number 20 has 20 electrons and has 2 valence electrons which it can lose to for stable
ion. The valence elctrons are present in valence shell i.e. 4s.

