You can never prove that something doesn't exist.
Saying that God doesn't exist is as empirically impossible to substaniate as is the belief that God does exist. In either case it requires the scientific validation of something wholly beyond the realm of science.
Not really. One doesn’t have to prove anything to believe in God or not believe in God. Atheists believe God doesn’t exist and are thus atheists. Christians can’t prove God exists. They believe it through faith. No proof required.