Final answer:
A double bond must exist between the two carbon atoms.
Step-by-step explanation:
A double bond in chemistry refers to a type of covalent bond formed between two carbon atoms. In a double bond, two pairs of electrons are shared between the carbon atoms, resulting in a stronger and more stable connection compared to a single bond. This bond is typically represented in chemical structures by a double line (═) between the two carbon atoms.
Double bonds play a crucial role in the structure of organic compounds, influencing their reactivity, physical properties, and overall behavior in chemical reactions. Examples of compounds with double bonds include alkenes, which are hydrocarbons containing carbon-carbon double bonds.