We will be arriving in Brussels airport on a Monday afternoon in September and plan to take a train to Ghent. I understand there is a train station in the airport and that I do not need to make reservations or purchase tickets ahead of time. My question: will we have to take a train from the airport to the central station and then another train to Ghent or is it possible to take a train from the airport to Ghent and not have to change trains? Thank you.
It depends on the time; some go direct some require transfer in Brussels.
It looks like there maybe one or two trains an hour going direct from the airport to Ghent. It takes 50 minutes.
You can search to see what it looks like for September
https://www.belgiantrain.be/en?journey=0