These are important questions, that only God can answer and God alone. Who can know the "mind" of God or the depths of God's mercy?
It seems that Pope Francis who tries to be inclusive and pastoral (which is good) opened "a can of worms" recently when he gave a homily to Vatican employees in the chapel of the Domus Santa Marta residence inside the Vatican grounds, where he chooses to live. These controversial remarks made headlines, "The Lord has redeemed all of us, all of us, with the blood of Christ, all of us, not just Catholics, Everyone! 'Father the atheists?' Even the atheists. And this blood makes us children of God of the first class. We are created children in the likeness of God and the blood of Christ has redeemed us all. And we all have a duty to do good".............This was not the first time I heard this idea. I heard it before and I believe the idea comes from Karl Rahner, that brilliant Jesuit theologian and it's called the "anonymous Christian." According to Rahner, we are all saved by the blood of Christ, by his redemptive act of love for humankind, whether we accept it or not, or profess it or not. So Pope Francis obviously knows about the writings of Karl Rahner and was influenced by them in what he said.
The Vatican has tried to clarify the Pope's remarks. Pope Francis is doing such a good job, is much loved already and is so well liked but he has to be careful what he says, after all he's the Pope and every word he says is scrutinized.
When I was in college I took a psychology course and I did a research paper on near death experiences. Even then there were thousands of accounts of people who were pronounced dead but were resuscitated and brought back to life. Many had a story to tell. Their experiences vary but there are similarities. They tell of feeling their souls leave their bodies, seeing the doctors and nurses trying to bring them back to life, feeling themselves at total peace, seeing a bright light, a tunnel, deceased relatives.............some people hear soothing music, feel being drawn towards God. No one ever wants to come back to life, each person feels like they must live a more fulfilled and meaningful life after the near death experience. Of all the accounts I've read, not one person, claimed to go to Hell, see or feel anything evil or have a negative, unpleasant experience.
So who knows? I'm sure hell exists for the very evil and our Church teaching says that it does. But will atheists go to hell, because they question God's existence, would a merciful God do that? You can answer that for yourself.