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Lewri t1_iy9nybs wrote

Reply to comment by drafterman in ELI5: why 2 hydrogen atoms hold more energy and less mass than 1 helium atom? by TheLapisBee

This answer is wrong. Deuterium and tritium are just as much hydrogen as protium is, and similarly helium includes helium-3 as well as helium-4. Further, deuterium has a mass of 2,014,101.777844 µu, while helium-4 has a mass of 4,002,603.254130 µu, so we can see that even when the number of protons and neutrons line up, the mass is not the same.

As you can see from the numbers I just posted, you and OP (u/TheLapisBee) are actually also backwards in that 2 ^(2)H atoms have more mass than 1 ^(4)He atom.

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TheLapisBee OP t1_iy9phip wrote

Oh wow! I was very much wrong... So where does this mass come from in the fusion process?

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Lewri t1_iy9qo7c wrote

>So where does this mass come from in the fusion process?

The product has less mass than the ingredients. Mass is being lost, not gained, so the question is where does the mass go.

The answer to where the mass goes is that it goes to the energy of the radiation being emitted.

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TheLapisBee OP t1_iy9r2n3 wrote

Ohhhh right, got a bit confused, thanks! Also how do u highlight what part of my comment you reply to?

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Lewri t1_iy9rv39 wrote

Depends if you're using markdown or the "Fancy Pants Editor". In Markdown you simply put a > at the start of the paragraph, like this:

>This is a quote

In the "Fancy Pants Editor" you have to select the quote block option through the GUI.

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drafterman t1_iy9pr6l wrote

Sans clarification/qualification, it is not unreasonable to treat hydrogen as hydrogen-1 and helium as helium-4.

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