Describe the mechanism for bromination across a double bond

This mechanism is an example of an electrophillic addition reaction.

Firstly consider the approach of a Br2, and how that bond will develop an induced dipole as a result of the high electron density on the double bond.

Use curly arrows to show how the double bond 'attacks' the partially positive bromine, and how this causes the Br-Br bond to break heterolytically. Overall we have formed a new C-Br bond and a Br anion. But, we must remember to always conserve charge- therefore remembering the carbocation generated.

The final step involves the bromine anion attacking the carbocation, forming the dibromo product.