Re: When our sun becomes a red giant, what will happen to our atoms?

What a fascinating question!

When the sun becomes a red giant in about 5 billion years, it is likely that the sun will swallow Earth and everything on it. The sun is so hot that everything will vaporize and break down into its constituent atoms. These atoms will stay in the outer layers of the sun, but it is possible that a few of them will get mixed into the core of the sun where nuclear reactions occur. If that happens, some of your atoms may take part in nuclear reactions and become different elements.

At this point the theories of astronomers are not precise enough to tell us if the sun will actually swallow Earth. During the last stages of the sun's evolution, the sun will loose mass. Earth will be less strongly attracted to the sun and move further away from the sun and avoid being swallowed. Exactly what will happen to Earth depends on how much mass the sun will loose.

Our sun will not become a nova; for that the sun would need a companion star, i.e., the sun would have to be part of a binary system. The sun also will not become a supernova and blow itself to pieces. The sun does not have enough mass for that to occur.

Reference: Any introductory astronomy text discussing stellar evolution, such as Foundations of Astronomy, 4^th edition, by M. Seeds, 1996, p. 265, or Discovering Astronomy, 3^rd ed, by Robbins, Jeffries, and Shawl, p.387