Final answer:
The ions Ca1- and S2+ do not occur because calcium normally loses two electrons to form Ca2+, and sulfur gains two electrons to form S2-, following the octet rule for stable electron configurations.
Step-by-step explanation:
The ions Ca1- and S2+ do not exist because of the ways that calcium (Ca) and sulfur (S) typically form ions. Calcium, a group 2 element, has a tendency to lose two electrons to achieve a noble gas electron configuration, resulting in a Ca2+ ion, not Ca1-. Sulfur, being in group 16, commonly gains two electrons to fill its valence shell, forming an S2- ion, not an S2+ ion. Ions must follow the octet rule, seeking to achieve a stable electronic configuration similar to the noble gases. Hence, Ca1- and S2+ do not occur because they would not fulfill the stable electron configurations dictated by their respective positions in the periodic table.