What is the force that holds atoms together in a substance?

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Main Question or Discussion Point

I know of the four fundamental forces ie the strong and weak nuclear forces, gravity and electromagnetism, but what is the force that holds atoms together in a substance and why is this force not considered a fundamental force?
 

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  • #2
f95toli
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The atoms in a substance are held together because of electromagnetic interactions, which as you point out is one of the four fundamental forces.
 
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Why is it then that the atoms of one substance don't bond with those of another, since the electromagnetic interactions between atoms would be common to all atoms
 
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malawi_glenn
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So you mean that molecules between different elements dont exist?
 
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So you mean that molecules between different elements dont exist?
I am not speaking of molecular bonding here. My question is regarding the force in any substance that holds the atoms or molecules together. For example what is the force that binds one iron atom with another iron atom and why isn't that same force capable of holding onto an atom or molecule of another substance, like an iron atom will not hold onto a copper atom.
 
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malawi_glenn
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iron can bond to copper.

It happens so that the electron clouds must fit, as in Lego roghly speaking. Some atoms electron clouds fits better with some kinds of atoms and worse with others. Thas has to do with the pauli prinicple, that states that no fermin can occupy the same quantum state. This is the thing that prevents the world from collapsing. If we not had the pauli principle, atomic nucleus would not exist, and all eletrons would be in lowest state and so on. The pauli principle is not a force, scince it does not comes from a potentail, nor it has exhange particles transmitting the field quanta.

And then you of course have competing forces in atom-bonding; at some temperatures atoms bond togheter and form a solid (helium becomes solid at very very low temperatures but mercury is liquid at room temperature)

The force that holds atoms in a crystal togheter is electromagnetic force, and the principle that prevents atoms to beeing to close (actually certain electron states) is the Pauli principle.
 

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