Can an atheist be ethical like theists

[robvalue]

This is rather a loaded question. A better question, from your point of view, would be why are atheists moral. Because quite clearly they can be, and are, on the whole.

But be careful not to conflate the morality which is concerned with well-being versus harm, and "religious morality" which involves a god being happy or unhappy about certain actions. They are not the same thing, so please be clear which are you talking about.

Yes, atheists can be moral just fine. I live in England where religion is virtually insignificant, and for the most part people behave well.

I've never been a theist, and I consider my morality to be extremely important. I'm constantly looking for ways I can improve it. I try my best to improve the world, to help people and animals where I can, and to reduce the amount of harm I cause. I don't need an imaginary being giving me commands to do this, nor do I need promises of heaven or threats of hell. The feeling that I'm doing the right thing is reward enough.

Evolution explains extremely well why we tend to have a sense of morality. We evolved as a cooperative species. Those that didn't cooperate fared less well so got less represented as time went on. This is a general trend of course, there is still a wide scope available. The fact that we tend to overlap a lot in our morality is explained by this, no appeal to magic is needed.