What significant contribution did lavoisier make to chemistry?

the answer to this question is He was the first to use scientific experiments to learn about atoms.
Before Lavoisier;s experiment, the concept of atom does not necessarily agreed upon by the chemistry experts because of no concrete proof for it.
This creates a chaotic situation in chemistry field when many scientists believed that they could change the core matters of certain objects. (They spent a huge amount of time trying to transform stones into gold due to unawareness of Atom)