When the neuron is at its resting potential the fluid inside the axon has what?

When a neuron is at its resting potential, the fluid inside the axon is rich in potassium ions (K+) and has a lower concentration of sodium ions (Na+). This creates a negative charge inside the neuron relative to the outside, typically around -70 mV. The resting potential is maintained by the sodium-potassium pump, which actively transports Na+ out of the cell and K+ into the cell, contributing to the overall ionic balance necessary for neuronal function.