What defines hydrocarbons?

Hydrocarbons are defined as molecules that consist of chains of carbon atoms bonded to hydrogen atoms. This characteristic structure allows hydrocarbons to vary in complexity, leading to different forms such as alkanes, alkenes, and alkynes. The primary feature of hydrocarbons is the carbon-hydrogen bond, which gives these compounds their unique chemical properties and reactivity.

The structure of hydrocarbons can range from simple molecules like methane (one carbon atom bonded to four hydrogen atoms) to complex structures such as those in fossil fuels and diverse organic compounds. The presence of only carbon and hydrogen in these molecules is what distinguishes them from other organic compounds that may include different elements, such as oxygen or nitrogen.

Other options describe different types of molecules: those bonded to oxygen or nitrogen would not fit the definition of hydrocarbons. Additionally, molecules lacking hydrogen atoms do not align with the hydrocarbon definition, as hydrogen is essential to their structure.