I'd say it's a little more complicated than this. In those fields where solid mathematical models have been developed, there's usually some back-and-forth between experimentalists and theoreticians, and any particular idea is usually considered mildly suspect until both rigorous mathematical models and solid empirical backing exist. New ideas might emerge either from the math or from empirical findings.

These days in physics and chemistry the mathematical models usually seem to emerge first, but that's not true for all fields; in astronomy, say, it's common for observations to go unexplained or to clank along with sketchy models for quite a while before the math properly catches up.