1. Let's assume the Bing Bang happened at second x, why didn't it happen before or after that specific time?
2. What initiated the Bing Bang?
If atheists claim that it was caused by a chemical reaction then where did all these molecules or chemical element come from in the 1st place? Moreover, isn't it ironic that they use the question 'who created God', yet, turn a blind eye at 'from where did the matter come?'.
First, thank you for the questions. It's said that you never truly understand a subject unless you can explain it to everyone, including your own grandmother, and I relish the opportunity to refine my knowledge by figuring out how to explain it.
First, I think I need to correct a misconception you seem to be expressing - the Big Bang didn't really involve molecules at all. It was more about subatomic particles, such as the quarks that make up the protons and neutrons that make up atoms that make up chemicals. There are immense and important differences between how things work on the level of molecules and how they work on the level of quarks, and trying to imagine the Big Bang as a chemical process leads to more incorrect inferences than imagining an atom is like a bun dotted with raisin-like electrons, the way atoms were once thought of.
That said, first causes /are/ an important topic. A technically correct answer is that the Big Bang theory isn't really /about/ what came before the Bang, any more than the theory of evolution by natural selection depends on the precise nature of how life came into being in the first place. All the Big Bang theory is /really/ about is the observation that all the galaxies we can see are rushing away from each other at particular speeds, and by figuring out where they used to be, it turns out that at a particular time they used to be smooshed together in the same place. We know enough physics to describe a lot of details about that smooshing, all the way back to when everything was an extremely tiny, extremely hot, extremely energetic particle-thingy smaller than a single atom. However, as to what happened before that, or what caused that to happen, the most accurate answer is that we don't have enough evidence to distinguish between which theories are more likely to be correct than others.
/That/ said, I have a personal favorite of a theory of what happened 'before the Big Bang' and what caused it; and the reason I prefer it is because it is based on observations of a particular phenomena that happens all the time, everywhere, and thus doesn't require many additional postulations. There's a physical process called 'virtual particles', described at
http://en.wikipedia.org/wiki/Virtual_particle , in which, usually, a particle and its anti-particle will pop into existence out of nothingness, exist for a brief fraction of a second, and then collide with each other and vanish back into nothingness. These virtual particles are appearing in massive quantities right in the space around you, in numbers high enough that they can be detected in various ways, causing various effects, such as the Coulomb force, the magnetic field, the strong and weak nuclear forces that hold atoms together, and more. More interestingly, occasionally these particles /don't/ bump back into each other and vanish, but get separated from each other and become ordinary, long-lived particles just like any other; this is what causes Hawking radiation around black holes.
Virtual particles are an epitome of the uncaused cause - they appear unpredictably, essentially at random. In a bit of space, there will be nothing, and then, suddenly, there will be /something/. Such creation isn't a singular event in the past - it is happening all the time, all around us, and is part of normal life.
And, as the most interesting part of this... there is no theoretical limit to how much energy such uncaused virtual particles can contain. Higher-energy particles seem to appear more rarely than lower-energy ones, but it is entirely feasible that, at any moment, there will suddenly appear a virtual particle containing as much energy as is in our entire universe, which will avoid immediate collision with its counterpart, and will then go on to start expanding and breaking apart into a host of smaller particles... a process which, as far as I can tell, would be indistinguishable from the Big Bang as we know it.
I'm not saying that this /is/, definitively, how the Big Bang happened. But it's a /possible/ answer. If it's proven right, then Yay! And if it's proven wrong, then hey, it's just a theory, and there are plenty more where it came from.
