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# Do all isolated nucleons have the same mass? Watch

1. I'm doing my notes on binding energy, fusion etc, I just needed to clarify this. I'm assuming it to be true because it just seems logical, but I want to be sure.
Nucleons lose some mass(energy) when they bind to form nuclei. So the mass of any unbound, isolated nucleon is always the same, right?
2. No because nucleus have a different proton numbers. Oxygen has 8 protons and carbon 6 protons and Hydrogen 1 proton. This is complementary to the number of electrons the nucleus of each atom has. The mass of nucleus is made up of neutron and proton amounts. The neutron number is the atomic mass minimize the proton number.
3. (Original post by gloria97)
I'm doing my notes on binding energy, fusion etc, I just needed to clarify this. I'm assuming it to be true because it just seems logical, but I want to be sure.
Nucleons lose some mass(energy) when they bind to form nuclei. So the mass of any unbound, isolated nucleon is always the same, right?
(Original post by HYI52N)
No because nucleus have a different proton numbers. Oxygen has 8 protons and carbon 6 protons and Hydrogen 1 proton. This is complementary to the number of electrons the nucleus of each atom has. The mass of nucleus is made up of neutron and proton amounts. The neutron number is the atomic mass minimize the proton number.
I think OP was referring to nucleons, not nuclei.

Just to clarify, are you referring to the particles which make up the nucleus (i.e. neutrons and protons) having the same mass when isolated?
If so, then yes, it's true that both of these particles will lose mass-energy when bound by the strong interaction, as you stated. If you consider a neutron/proton completely isolated, at rest, than that is a constant value.

As another note, because you're referring to both neutrons and protons at once: both particles have a constant rest mass (given on exam data sheets), which states their mass when completely isolated and at complete rest (because if the particle's moving, then its mass will begin to alter as per relativity). Neutrons and protons have very similar but different rest masses:

Proton: 1.672621777(74)×10−27 kg
Neutron: 1.674927351(74)×10−27 kg

Neutrons are slightly more massive than protons. However, the values are equal to 3 significant figures, which you'll probably seldom need to work beyond.
4. (Original post by HYI52N)
No because nucleus have a different proton numbers. Oxygen has 8 protons and carbon 6 protons and Hydrogen 1 proton. This is complementary to the number of electrons the nucleus of each atom has. The mass of nucleus is made up of neutron and proton amounts. The neutron number is the atomic mass minimize the proton number.
(Original post by sjgriffiths)
I think OP was referring to nucleons, not nuclei.

Just to clarify, are you referring to the particles which make up the nucleus (i.e. neutrons and protons) having the same mass when isolated?
If so, then yes, it's true that both of these particles will lose mass-energy when bound by the strong interaction, as you stated. If you consider a neutron/proton completely isolated, at rest, than that is a constant value.

As another note, because you're referring to both neutrons and protons at once: both particles have a constant rest mass (given on exam data sheets), which states their mass when completely isolated and at complete rest (because if the particle's moving, then its mass will begin to alter as per relativity). Neutrons and protons have very similar but different rest masses:

Proton: 1.672621777(74)×10−27 kg
Neutron: 1.674927351(74)×10−27 kg

Neutrons are slightly more massive than protons. However, the values are equal to 3 significant figures, which you'll probably seldom need to work beyond.
Yeah, I was referring to neutrons and protons. I'm glad that's clarified, thank you

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