what is released when the chemical bond is broken between the second and third phosphates of an atp molecule

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.

High-energy and unstable.

Ok so co(g) is not pronoused that. the only clue is that youpronouse it the oppisote way. 

Ibelieve it is b. proton.hope my answer has you : )