* The Periodic Table: The periodic table organizes all the known chemical elements, which are pure substances that cannot be broken down further by chemical means.

* Natural Gas: Natural gas is a mixture of different hydrocarbons, primarily methane (CH4), but also containing varying amounts of ethane, propane, butane, and other gases.

In summary: Natural gas is a complex mixture of compounds, not a single element like those found on the periodic table.