Definition of atheism
1. archaic : ungodliness, wickedness
2. a : a disbelief in the existence of deity
b : the doctrine that there is no deity
Here is a very good web page to answer back atheism’s claim by a philosopher Peter Kreeft.
If you want a scientists point of view, someone who was an atheist converted to Christianity here is Francis Collins PBS conversion here.
Another famous priest and scientist that I like is Fr. Robert Spitzer. He has his interview here.