They want to come close. So in order for me to move this guy a distance R here a distance two R from our nucleus. That means I have to do work on that electron. So if We Consider Our Proton And our electron a system, that means I have to do work on my system to move this electron a distance r away from this electron, right? So that means work must be done on our system. And because work is a transfer of energy, energy must be transferred into our system.