Trans-1,2-Dibromoethylene(trans-C2H2Br2) is non-polar, while Cis-C2H2Br2 is polar.

The polarity of C2H2Br2 depends on the arrangement of hydrogen and bromine atoms around the C=C double covalent bond.

1,2 dibromoethene (C2H2Br2) consists of a C=C double bond, two C-H single bonds, and two C-Br bonds.

In this trans configuration, the two bulky and electronegative bromine atoms are positioned on opposite sides of the carbon-carbon double bond, perfectly canceling out their individual bond dipoles. The geometry around each carbon atom is trigonal planar, resulting in a flat, symmetrical molecule.

In cis-1,2-dibromoethene, the unequal dipole moments of C-H and C-Br bonds do not get canceled equally.

Thus it is overall polar (net μ > 0).

Contrarily, in trans-1,2-dibromoethene, the more electronegative Br-atoms are located directly opposite to each other.

Therefore, the C-H and C-Br dipole moments get canceled equally with the corresponding C-H and C-Br dipole moments, respectively, resulting in a non-polar molecule overall (net μ = 0).