During the action potential of a neuron, which ion is primarily crossing the membrane during the depolarization phase, and in which direction is the ion moving?

The answer is Na + is entering the cell and the K + is leaving, during the depolarization phase of the action potential open Na + channels allow Na + ions to diffuse into the cell. This inward movement of positive charge makes the membrane potential more positive. The depolarization phase is a positive response sequence where open Na + channels cause depolarization which in re-occurrence causes more voltage gated Na+ channels to open. 

The answer is overmatching