In a famous experiment with a balloon and wool. http://phet.colorado.edu/sims/html/...atest/balloons-and-static-electricity_en.html Initially the balloon and wool pullover have no ions. I understand how positive ions are formed, that you apply energy to the electron, thus electron overcomes the attracted force created by a proton, but how are the negative ions created? I assume when we rub the balloon with a wool pullover we apply energy to both materials, thus depending on a material (how tight electrons to the nucleus) electrons are escaped from both materials forming positive ions. BUT, I dont understand how the negative ions created, why would atom which is in equilibrium get more electrons and why at the end we get 2 charged materials?