Here are some important questions to ask yourself when you are dating:

How do you feel when you’re with him?
Are you comfortable with yourself in his presence?
Are you self conscious?
Are you worried about how you look?
Are you concerned about saying something smart or funny?

Good chemistry means that you make each other feel comfortable being yourselves.
This won’t usually happen on the first date, it can happen on the second or third etc.
He might make other people feel good when they are around him, but you need to think about how he makes you feel about yourself when you are around him.
If you come home thinking that the date was really nice, and you don’t feel tension – that’s good chemistry.
If you come home talking about him and the things you admire about him, then good for him for having all those good qualities – but how does he make you feel?
Coming home feeling good, relaxed, comfortable with yourself and confident is a sign that there was good chemistry.