Does the nucleus of an atom affect spacetime curvature inside the atom? If so, how does this affect the electrons and other atoms?
It does bend the space around the electrons but the effect on the curvature of spacetime is so minuscule that it has almost no effect on the electron orbits. ( dictated by General Relativity)
At that level( state of the atom including mass of nucleus and the distance of electrons to nucleus ) the electromagnetic force is far stronger than gravitational force and hence its effect is almost negligible.