A carbon atom can become the negative end of a bond when it is bonded to an electronegative element. Electronegativity is the ability of an atom to attract electrons towards itself. When a carbon atom is bonded to an electronegative element, the electronegative element attracts the electrons in the bond more strongly, making the carbon atom relatively negative.

Some electronegative elements that carbon can bond to include:

- Oxygen (O)

- Fluorine (F)

- Chlorine (Cl)

- Bromine (Br)

- Iodine (I)

In general, the more electronegative the element, the more negative the carbon atom will become.