Nuclear sizes are expressed in a unit named

Nucleus and its size

1. Basically, the nucleus is the center of an atom, where the protons and neutrons are concentrated.
2. The size of a nucleus is around ${10}^{-16}m$ to ${10}^{-15}m$.

Unit of nuclear size measurement

1. Fermi is the unit, which measures the microscopic distances, like the radius of a nucleus, atom, etc.
2. $1fermi={10}^{-15}m$, which is a very small unit.

So, the nuclear sizes are expressed in a unit named fermi.