In a molecule of calcium sulfide, calcium has two valence electron bonds, and a sulfur atom has six valence electrons. How many lone pairs of electrons are present in the Lewis structure of calcium sulfide? A. one
B. two
C. three
D. four
E. none

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