Will this FX lens work on my Nikon D3100?

This lens http://robertscamera.com/photo/lenses/for-slrs-dslrs/primes/af-s-nikkor-50mm-f-1-8g.html is advertised of having FX format, while my Nikon D3100 is DX format. The lens, as advertised, is compatible with DX, FX, and FX in DX crop mode. Would this work on my D3100? How would this affect the camera operation, especially the aperture control?

Yes, it will be compatible. FX lenses can be put on DX cameras. This particular model is AF-S, so it will autofocus on the D3100. (There's a 50mm f1.8 AF-D model that won't.)

DX format is a smaller one than FX - so a FX lens can fill the frame of a DX camera without any difficulties. A DX lens on a FX camera on the other hand can't fill the whole frame, so the camera automatically crops from the middle.

In other words, FX lenses can be used on DX cameras without drawbacks. Be aware that many old FX lenses do not have an autofocus motor in the lens (called AF instead of the newer AF-S) and thus won't autofocus on cameras that don't have an autofocus motor in the body. You'll need AF-S lenses, not AF ones, for your camera, just like the one that you linked to is.It'll work perfectly.

So… Yes it will work perfectly on your camera. The aperture control won't be affected at all.It'll open up all the way to f/1.8 as that's something that relates to the focal length. The sensor format has nothing to do with it.

The Nikon AF-S 50mm f1.8G will be fine on your D3100. Enjoy.

Works fine. Only difference is that you have a field of view that's equivelant to a 75mm.

Now, put your 18-55 on 50mm. That's the field of view you have with this lens. Only instead of a f5.6 aperture you can go to f1.8