If an atom has 28 protons and 29 neutrons, what is the mass?

What happened to the amount of carbon dioxide in the atmosphere from 2010–2017?

Why does earth rotate? because earth is formed from cold gases collapsing due to gravity because the matter in the nebula that formed earth was spinning because earth forms more than 99% of the mass of the solar system because the hydrogen atoms inside the nebula fused to form helium

Which of the four hypothetical substances you investigated would be most harmful to living organisms? 50 points!