Assamualaykum..
Ask anyone the question: "Do u believe in God?" and you are sure to recieve a variety of answers. The question should be "What do you believe about God?"
Think about this, If there is a creation, there must be a Creator, if there is a Creator, He must be the Sustainer. The Creator cannot create Himself. If He is the sole Creator/Sustainer, He must be ONE.
In other word, God must be ONE. Otherwise we would see great differences and competition between the gods if there were one -- Alone.
Do we agree that this is a creation? Or do we accept that nothing came out of nothing to form this entire universe? Something does not come out of nothing. So, there must be something in existance already which created all that upon in times of need and thanksgiving. As Allah has said in His Holy Quran: "I only created you all to worship me alone."
He also says that we are all being tested by Him with regard to our wealth, families, children and social status.
There are alot of scientific explaination in the Quran that has proved God's existance.here are some of the verses.
The Quran on origin of the universe
Then He turned to heavens when it was smoke..(Quran 41:11)
Have not those who disbelieved known that the heavens and the earth were one connected entity, then We separated them?.. (Quran 21:30)
Quran on clouds
Have you not seen how God makes the clouds move gently, then joins them together, then make them into a stacks, and then you see the rain comes out of it.. (Quran 24:43)
Quran about hails and lightning
..And he sends down hail from mountains (clouds) in the sky, and He strikes with it whomever He wills, and turns it from whomever He wills. The vivid flash of its lightning nearly blinds the sight. (Quran 24:43)
Quran on deep sea and internal waves
Or (the unbelievers' state) is like the darkness in a deep sea. It is covered by waves, above which are waves, above which are clouds. Darkness, one above another. If a man stretches out his hand, he cannot see it... (Quran 24:40)
Quran on Human Embryonic Development
We created man from an extract of clay. Then We made him as a drop in a place of settlement, firmly fixed. Then We made the drop into an alaqah(leech,suspended thing,and blood clot),then We made the alaqah into a mudghah(chewed-like substance)..(Quran 23:12-14)
Quran on Cerebrum
Let him beware! If he does not stop, We will take him by the Naseyah(front of the head) a lying,sinful Naseyah (from of the head)! (Quran 96:15-16)
I hope this will answers to the Atheist. But if it still wont convinced the Atheist. Try this,
The pattern of air tubes in the Lungs of all human being s make the sentence "There is no god but God, and Muhammad is the Messenger of God" in arabic.Go on and make the research .