“Atheists cannot prove that there is no God...”
You cannot prove a negative. That is why agnosticism is a more logical system than atheism.
Sure you can in many instances. I can prove I don't have a pistol in my front left pocket by turning the pocket inside out. In this instance, however, you can't prove or disprove the existence of God. This is by definition as God transcends the empirical bounds which restrain the concept of "science" or "reason". "Finitum non capax infinitium." Each side to the argument must rely on trying to establish the greatest probability for their position.