Answer:
![CaS](https://img.qammunity.org/2021/formulas/chemistry/high-school/71nydvnrg6g64s7bz64sjgc1z9zvpuy4y5.png)
Step-by-step explanation:
Hello!
In this case, since calcium's oxidation state when forming ionic bonds is +2 and sulfur's oxidation state when bonding those bonds is -2, for the required formula we write:
![Ca^(2+)S^(2-)](https://img.qammunity.org/2021/formulas/chemistry/college/2lug0sj7w2q0y7a7pg55k0go0ldcymvicp.png)
Now, since they have the same charge number, we infer the ionic compound formed when they bond is calcium sulfide:
![CaS](https://img.qammunity.org/2021/formulas/chemistry/high-school/71nydvnrg6g64s7bz64sjgc1z9zvpuy4y5.png)
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