Carbon also has 4 valence electrons that are available for bonding. Most elements have only one or two or three. The active nonmetals hold electrons so strongly that they usually don't form covalent bonds with other elements. Organic compounds tend to be nonpolar and tend to react slowly unless heated. When organic compounds are heated, they tend to become unstable and increase their reachion rates with oxygen in the air to produce burning.
Hydrocarbons are a group of organic compounds containing only carbon and hydrogen.
These are primary constitutients of oil and natural gas. Because these gases are odorless in their pure state, the garlic odored phosphorus hydride is often added to natural gas so that leaks can be easily detected by their odor. Thus it bubbles up in swamps, dumps, stagnant pools, etc. The low boiling point alkanes come off first and are condensed. Then the higher boiling point gasoline fraction boils off.