Both the electron and the proton exert equal electrostatic forces on each other. This is due to Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction.

Here's why:

* Electrostatic Force: The force between two charged particles is directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

* Equal and Opposite: The electron and proton have equal but opposite charges. This means the force experienced by the electron due to the proton is the same in magnitude but opposite in direction to the force experienced by the proton due to the electron.

Therefore, while the electron is much lighter than the proton, the electrostatic forces they exert on each other are equal and opposite.