Curved arrow [ENDORSED]

[DanielLee3H]

What exactly does the curved arrow mean when it starts at a single bond and points to an atom or molecule? I get that the bond is breaking and forming around the new atom but does each atom bonded originally take one of the electrons (so does it like split down the middle?). Or do both electrons that were being shared both go to the atom being pointed at?

[garrett_perozich]

Curved arrows are used to represent the transfer of a pair of electrons. So while it may be used for a bond, in which case it would represent the transfer of the two electrons that are being shared between the atoms for that particular bond, it may also be used on a lone pair of electrons, in which case it would represent the transfer of that specific pair of electrons.