Which of the following is a heterogeneous mixture?

Which function is performed by earths atmosphere? a. ultraviolet rays are prevented from reaching the ozone layer. b. earths temperature is raised and moderated by trapping in heat c. charged particles from the sun are prevented from reaching earth. d. magnetic charges from space are prevented from reaching earths surface.

Air can be considered a mixture. which statement does not explain why?

The atom fluorine generally will become stable through the formation of an ionic chemical compound by accepting electron(s) from another atom. this process will fill its outer energy level of electrons.