I have a verizon iphone 5 sim card. Will it work in an unlocked AT&T iphone 4s?

I know that they are different sizes, but i have a converter to overcome that obstacle so that is not the issue. I'm simply asking will the phone actually be able to be activated on the verizon network?

No, it would not work on an AT&T iPhone 4S, because AT&T uses different 4G frequencies than those of Verizon, so I would say no.