Described atoms as having a positive nucleus with electrons that have different energies at different distances from the nucleus.

If you want to know who that person is, then the correct answer is Niels Bohr.
Niels Bohr described atoms as having a positive nucleus with electrons that have different energies at different distances from the nucleus.
He was a famous Danish physicist whom we can thank for groundbreaking discoveries regarding quantum physics. 

Elias is almost correct. he just got it backwards.the correct answer is that it demonstrates elastic potential energy transforming into kinetic energy.