Answer: 4s orbital contains the electron that calcium loses to form an ion
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 [tex]Ca^{2+}[/tex] ion. The valence elctrons are present in valence shell i.e. 4s.
[tex]Ca:20:1s^22s^22p^63s^23p^64s^2[/tex]
[tex]Ca^{2+}:18:1s^22s^22p^63s^23p^64s^0[/tex]
