* Ionic Compounds: The compounds listed are all ionic compounds, meaning they are formed by the electrostatic attraction between positively charged ions (cations) and negatively charged ions (anions).

* Predicting Stability: The stability of ionic compounds is generally influenced by the following factors:

* Electrostatic Attraction: Stronger electrostatic attractions between ions lead to more stable compounds. This is related to the charges of the ions and their size.

* Lattice Energy: This is a measure of the energy released when ions come together to form a crystal lattice. Higher lattice energy generally indicates a more stable compound.

* Analyzing the Compounds:

* SrCl: Strontium (Sr) is in group 2, forming a +2 ion (Sr²⁺). Chlorine (Cl) is in group 17, forming a -1 ion (Cl⁻). The formula for strontium chloride is SrCl₂, not SrCl. This compound is stable.

* AlF₂: Aluminum (Al) is in group 13, forming a +3 ion (Al³⁺). Fluorine (F) is in group 17, forming a -1 ion (F⁻). The formula for aluminum fluoride is AlF₃, not AlF₂. This compound is also stable.

* BaS: Barium (Ba) is in group 2, forming a +2 ion (Ba²⁺). Sulfur (S) is in group 16, forming a -2 ion (S²⁻). This formula is correct, and this compound is stable.

Conclusion:

* SrCl₂ (Strontium Chloride)

* AlF₃ (Aluminum Fluoride)

* BaS (Barium Sulfide)

All three of these compounds are stable. Remember to always double-check the formulas based on the charges of the ions involved.