Sehsr
I really couldn't tell you why you have Hornets around your impatiens. Hornets usually like eating other insects, could be worms among the leaves. They use these to feed their young. If they are going into the flowers they are more then likely a type of bee.

I had some Impatiens glandulifera growing on my balcony during the summer and it was always covered in wasps and bees constantly feeding at the flowers. A colony of paper wasps actually set up a nest under a window ledge outside my 14th story apartment about 12 feet from the plants on my balcony.

Here is a link that might be useful: Paper wasps