What was the name for the spectrum of specific wavelengths produced by an existing element?

How has the scientific community addressed the safety of chemicals? a. chemicals are repeatedly tested, even those that have existed for a long time. b. existing chemicals are tested if they have never been tested before. c. chemicals are tested if they are suspected to have caused a problem. d. only new chemicals are tested.

Hey can you me with this i really need y’all

What are the major types of a chemical compound