The scientist who concluded that the nucleus of an atom contains a dense center of positive charge was Ernest Rutherford.

He conducted his famous gold foil experiment in 1911, which led him to this groundbreaking discovery. Here's a summary:

* The Experiment: Rutherford fired alpha particles (positively charged particles) at a thin sheet of gold foil.

* Unexpected Results: Most of the alpha particles passed straight through the foil, but a small number were deflected at large angles, and some even bounced back.

* Rutherford's Interpretation: Rutherford concluded that the atom must have a small, dense, positively charged center that was responsible for deflecting the alpha particles. This center was named the nucleus.

This experiment revolutionized our understanding of the atom and paved the way for future discoveries in nuclear physics.