Entropy

[Orly Termeie 3I]

Why does entropy decrease when bonds are formed?

[Anthony Rosas 2K]

Entropy is spontaneity. So when two atoms are bonded, they are less free. Hence, there is less spontaneity and entropy decreases.

[Helen Meng 2J]

Another way to think of it is that entropy measures the "disorder" of the reaction. If two reactants are being bonded together to form a product, there are fewer total molecules moving around, meaning there is less disorder. This is why gases have higher entropy than solids, since gas molecules are able to occupy the space of whatever container they happen to be in while solids are conformed to a certain shape by strong intermolecular bonds. This means gas molecules have greater disorder, and have more molecules moving around. Similarly, when a bond is formed between two reactants, the product has fewer molecules moving around and creating "disorder", thus decreasing the entropy.