The first two techniques are essentially upgraded versions of ones you have previously taught me, so the strengthens and weaknesses should still apply just to a higher degree.
Desmond then holds up his right hand releasing dark chakra into it and shaping it into a sphere similar to how he would perform rasengan. Unlike the rasengan, however, this jutsu would be a dark purple or black in color and have two rings around it giving it the look of an atom.
Nice.
said, Desmond, as he slammed the atom into a nearby rock shattering it and scattering its pieces across the training field.
This like you said is essentially the dark version of the rasengan and such would act the same but with the addition of dark releases released form strengths and weaknesses if I'm not mistaken.