Question

Are the three isomers for C2H2F2:

cis-1,2-difluroethylene
trans- 1,2-difluroethylene
1,1-difluroethylene or 1,2-difluroethylene

or all these all the wrong names.

Answer 1

Since you don't draw the structures (and it's almost impossible to do it on these boards) I can't tell you if the name is correct or not. However,
there is a cis-1,2-difluoroethylene, a trans-1,2-difluoroethylene, and a 1,1-difluoroethylene. The name of 1,2-difluoroethylene isn't complete; i.e., it needs to be preceded with a cis or a trans designation. That gives you the three isomers.