Actually, you need to look a little deeper into modern science before you claim to know what atheists believe. Modern scientific research shows us that more than likely there is no "such thing as nothing". The Higgs field pervades all of space-time, the universe is and always has been composed mainly of dark matter and energy (of which we know almost nothing about its properties) rather than the "ordinary matter" that composes us and the world we know. It is proven that space is constantly expanding and that it can be warped by massive objects.
In short, modern physics has proven that a "vacuum" is full of electromagnetic waves, which can never be completely eliminated. In short there is no such "thing" as "nothing" and never was.