Before the 1950s, archaeologists had no opportunity to think about absolout dates about the cultures they concerned. After W.F. Libby invented the C-14 dating, it all changed the archaeology (and also he got Nobel Prize for it). Because with this method, a trustable timescale added to archaeological data which had changed almost all theories.
Before the invention of that chemical method, all chronologies were relative. As archaeologists saw a piece of pottery (for example) more primitive than the other, they put that to an earlier era than the other. But with C-14 dating, it became possible to undenstand that it could be at the same age or even younger. Today more than 100 chemistry laboratories serving archaeologist with C-14 dating.
The C-14 is not the only chemical method that helps the archaeologist. It is the most important but there are many other chemistry methods in use today. For example, it is now possible to understand what some containers included before they have been burried under the soil, and also chemistry helps archaeologists and conservationist to protect and reconstruct their findings.