an electron and a proton are initially very far apart (effectively an infinite distance apart.) they are then brought together to form a hydrogen atom, in which the electron orbits the proton at an average distance of 5.29 x 10 -11 m. what is EPE final - EPE initial, which is the change in the electric potential energy?

Answer 1

The electrical potential energy is a negative number,
-k e^2/a

where a is the orbit radius (which you have been given), e is the electron (and proton) charge, and k is the Coulomb's Law constant.