Static Electricity - Mission SE3 Detailed Help

Material X and material Y are rubbed together. As a result, material X acquires a negative charge. This means that ______.

Triboelectric Charging
Triboelectric charging (a.k.a., charging by friction) is the charging process that usually involves the rubbing together of two objects of dissimilar materials in order to transfer electrons from one object to the other. The object made of the material with the greatest affinity for electrons is the object that receives the electrons; the object with the lesser affinity for electrons provides the electrons. The process usually involves the rubbing of the two materials because it increases the amount of close intimate contact between the different atoms and allows for more electrons to be transferred.

If material X becomes charged negatively when rubbed with material Y, then it gained electrons from material Y. This occurs because their atoms were in close intimate contact, allowing the more electron-loving material to draw electrons off the least electron-loving material.