The idiomatic expression "certain chemistry" refers to a natural rapport, connection or bond between two people that is often difficult to define but can be easily recognized. Full definition
So, after you spend time with the sugar mamma in an informal setting and develop certain chemistry, invite her to the special dinner. (sugarmammadating.org)
«There has to be a certain chemistry in the inner circle, and for him to choose those people in six weeks is a short time frame.» (canadianbusiness.com)
«In all these things it was professional, but there's a certain chemistry with people,» he said, according to the excellent blow - by - blow coverage on Re / Code. (inc.com)