Atheists: How did the first physical particle in the universe come into existence?

In order to disprove God, you need to prove that "NOTHING" exists..and mathematics, physics and any given science says that "nothing" does not exist...but atheists reject God anyway, they can not disprove God, yet they are arrogant enough to reject God..they believe in nothing while "nothing" does not exist, you guys disappoint me. No matter how small you slice the physical universe down to, it cannot find its explanation for its existence in itself, something outside had to create it, as natural causes didn't exist yet.