For 10 points, name this dense region at the center of an atom composed of protons and neutrons.
Rare examples can contain hyperons, while those with radii substantially larger than predicted by the liquid drop model are called "halo" examples. The interaction between their components can be modeled by a screened Coulomb potential named for Yukawa. Their composition is defined by certain (*) "magic numbers" that deviate from the semi-empirical mass formula by having unusually large average binding energy. The existence of this entity was demonstrated by the gold foil experiment. For 10 points, name this dense region at the center of an atom composed of protons and neutrons.
Rare examples can contain hyperons, while those with radii substantially larger than predicted by the liquid drop model are called "halo" examples.
{nucleus}