Which of the following polyatomic ions will form an ionic compound with a single sodium ion? co₂2-
PO4^3-
S04^2-
NO₃²-

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