One model for the potential energy of a two-atom molecule, where the atoms are separated by a distance r, is U(r)=Uo((ro/r)11−(ro/r)5) where r0 = 0.70 nm and U0 = 8.2 eV. Note: 1 eV = 1.6 x10^−19J.

You can use SI units, but CAPA will also accept these units that will simplify your calculations:

Force = eV/nm
Energy = eV
distance = nm

What is the distance between the atoms when the molecule is in stable equilibrium?