Final answer:
The Ca2+ ion shares the same electron configuration as argon (Ar), a noble gas in Group 0, thereby making them isoelectronic.
Step-by-step explanation:
The Ca2+ species is electronically similar to the elements in Group 0, the noble gases. Specifically, when calcium loses its two valence electrons to form Ca2+, it achieves the same electron configuration as argon (Ar), which is a noble gas. Calcium is in Group 2 of the periodic table, and has a ground state electron configuration of 1s²2s²2p⁶3s²3p⁶4s². Losing the two electrons in the 4s subshell, calcium becomes Ca2+ with an electron configuration of 1s²2s²2p⁶3s²3p⁶, which is exactly the configuration of the noble gas argon, indicating that they are isoelectronic.