What does the quantum-mechanical model of the atom tell you about the location of an electron in an atom?

Answer 1

It tells you that it's exact location cannot be determined, but that it's probable location(s) can be calculated.

Answer 2

It tells you that the electron is not located on a stable trajectory but can be with a very small probability everywhere in space excepted the nodal points where the probability is zero

All the orbitals except the spherical s (l=0) have a nodal point in the nucleus. This means that only electrons "s" can be in the nucleus. This is the basis of Mössbauer spectroscopy