In the previous lesson, you learned that a redox reaction may be explained as a transfer of valence electrons from one substance to another. This transfer can be viewed as a competition for electrons. In other words, two entities compete for the same electrons. If one entity is able to pull electrons away from the other, a spontaneous reaction occurs. Recall the example from Lesson 1 in which a copper coil is immersed in a silver nitrate solution. In this example, a spontaneous redox reaction occurs because the electron-deficient silver ions have a stronger attraction for copper's electrons than the copper atoms does. In other words, the silver ions win the "tug of war" for electrons, and an electron transfer occurs.