Hello!

Molecule of a stability can be decided based on five factors-

1.Octet rule-it should have 8 valance electrons.

2.Minimal formal charge- molecules with more formal charge are less stable and vice versa.

3.if it's an electronegative element, more negative charge will make it more stable.

4.If there's a resonance, then it is said to be stable. So look at the resonance condition in the molecule.

Apart from these, look for Inductive effect in the molecules which decides the stability and allows u to compare various available molecules and decide the order.