If a neutral copper atom becomes an ion that has a charge of 2+, how many electrons does the resulting ion have? a31
b27
c29
d28

Which best describes the present-day universe? opaque, expanding very slowly, stars produce heavy elements transparent, expanding at an accelerated rate, stars produce heavy elements opaque, expanding at an accelerated rate, stars produce only hydrogen and helium transparent, expanding very slowly, stars produce only hydrogen and helium