Using electronegativity values, which of the following bonds is ionic?

Find the mass in grams of 1.37x1020 particles of h3po4

The fact that the total amount of energy in a system remains constant is a(n)

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