Final answer:
Both K+ and Ca2+ have lost electrons to match the electronic configuration of argon, which has 18 electrons. Therefore, the answer to the question is c. both a. and b.
Step-by-step explanation:
The question asks which ion has the same electronic configuration as argon. Argon (Ar) is a noble gas with an atomic number of 18, which means it has 18 electrons in its neutral state and has the electron configuration of [Ne]3s²3p¶. When we look at the ions mentioned:
- K+ (Potassium ion) has 19 protons and, as a positive ion, it will have lost one electron, thus having 18 electrons which matches the electronic count of Argon.
- Ca2+ (Calcium ion) also starts off with 20 protons and as a doubly positive ion, it loses two electrons, leaving it with 18 electrons, again the same as Argon.
So, both K+ and Ca2+ have lost enough electrons to have the same electronic configuration as argon, which is a full outer shell corresponding to 8 valence electrons (octet rule).
Therefore, the answer is: c. both a. and b.