Final answer:
The potassium ion (K+) would stop flowing inside the cell at around 52 mV, due to the balance of electrical charge at this membrane potential, which is near the potassium equilibrium potential.
Step-by-step explanation:
The ion that would stop flowing inside the cell at around 52 mV is the potassium ion (K+). During the resting potential, voltage-gated K+ channels are typically closed; however, once a certain membrane potential is reached, these channels can open allowing K+ to flow. Since the resting membrane potential of a neuron is usually around -70 mV, and potassium ions are more concentrated inside the cell, they will normally move out of the cell to balance the electrical charge. When the membrane potential reaches approximately +52 mV, which is close to the potassium equilibrium potential, the flow of potassium ions tends to stop because the driving force for K+ (the difference between the membrane potential and the K+ equilibrium potential) is greatly reduced.