The scientist who discovered that atoms have positive charges was Ernest Rutherford.

He conducted the famous gold foil experiment in 1911, which demonstrated that:

* Most alpha particles passed straight through the gold foil, suggesting that atoms are mostly empty space.

* A small number of alpha particles were deflected at large angles, indicating the presence of a dense, positively charged nucleus within the atom.

This experiment led Rutherford to propose the nuclear model of the atom, which states that atoms consist of a small, dense, positively charged nucleus surrounded by negatively charged electrons.