Which of these elements exists as a solid at room temp and pressure? chlorine, bromine and iodine. why?

In the analysis of hair and fiber samples, which does a compound comparison microscope allow for that a conventional compound microscope does not? a. simultaneous observation b. polarization c. fluorescence d. higher magnification

What is the lowest number energy level where a d sublevel is found

Chemistry worksheet - i am not sure what they are asking for exactly?