Any of a group of hydrocarbons that have carbon atoms in chains linked by single bonds and that have the general formula Cn H2n &sbplus;2 . Alkanes can be either gaseous, liquid, or solid. They occur naturally in petroleum and natural gas, and include methane, propane and butane. &diamf3; The group of alkanes as a whole is called the alkane series or the methane or paraffin series. Its first six members are methane, ethane, propane, butane, pentane, and hexane.