Final answer:
Potassium (K+) is the ion with the greatest influence on the resting membrane potential of neurons due to its higher membrane permeability and the role of the sodium-potassium pump in maintaining the potential.
Step-by-step explanation:
The ion with the greatest influence on the resting membrane potential of most neurons is Potassium (K+). Neurons maintain a negative charge inside during their resting state, around -70 millivolts relative to the outside. This resting membrane potential is mainly due to a higher permeability of the neuron's membrane to K+ compared to other ions, such as Na+. K+ moves out of the cell via potassium leakage channels more readily than Na+ moves in. This movement of K+ ions out of the cell contributes to the negative charge inside. Additionally, the sodium-potassium pump exchanges three Na+ ions out of the cell for every two K+ ions it brings in, which also helps maintain the resting membrane potential.