I don’t know what would be convincing experiments for atoms.
Assuming you convinced him of the epistemological primacy of experiment, I see two obvious paths:
The kinetic theory of gases, particularly the ideal gas law;
Stoichiometry in chemistry—for example, electrolysis of water.
I would add Brownian motion to that list.
Assuming you convinced him of the epistemological primacy of experiment, I see two obvious paths:
The kinetic theory of gases, particularly the ideal gas law;
Stoichiometry in chemistry—for example, electrolysis of water.
I would add Brownian motion to that list.