Can they find out if I am having a boy or girl at 16 weeks?

I am 15 weeks prenant and i have a sono on friday. ( I will be 16 weeks then) What are the chances of them finding out if i am having a boy or girl? As well do I have to put the fathers name on the birth certificate and what rights will he have to my child. We dont live together nor are we married. ( Never have Been! ) Will i have to give him visitation?