[yourheadsnotonright]

What is the maximum number of Cs+ ions that can be produced per joule of energy absorbed by a sample of gaseous Cs atoms?
Express your answer using four significant figures.

I got 1.683x10^18 ions but its the wrong answer. I attempted again and got 3.203x10^18, but its not the answer either
Can someone please explain how to do this and what the correct answer is? Thanks in advance.