What does electron affinity mean?

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.

In which block of the periodic table is uranium (u) found? s blockd blockp blockf block

What is the chemical formula of magnesium bromide? a. mgbr2 b. mgbr c. mg2br2 d. mg2br