What does the kinetic theory say about the kinetic energy present in solids

The kinetic energy of solids is limited to vibrational energies..the particles are tightly bound in their crystalline structure and can only bend, flex, and vibrate about relatively fixed position.  When vibrational energies exceed the strength of the force holding the particles together, the crystal structure collapses and we say the material melted.  The particles can now have, in addition to its vibrational energies, rotational energy.  Chunks of the collapsed crystal can, like a ball floating in water, rotate without showing much translational energy. Generally, we associate solids with vibrational kinetic energy, liquids with rotational kinetic energy, and gases with translational kinetic energy. Actually though, liquids have both vibrational and rotational energies, and gases have all three.

radioactive decay occurs in unstable atomic nuclei – that is, ones that don't have enough binding energy to hold

the nucleus together due to an excess of either protons or neutrons.

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