Answer:
Ca(II)S
Step-by-step explanation:
In CaS (Calcium Sulfide), calcium is a metallic element and thus it is rich in valence electron. The outer most shell of CaS consists of two valence electrons, thus it is required to lose two electron to become noble. While sulfur has six valence electron in its outermost shell, thus it is required to gain two electrons to become noble. Thus there is a sharing of two electrons between the two element and therefore its ionic formula is Ca(II)S