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How does the molecular formula C2H6 describe ethane?

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structural formulas of some organic compounds — organic compound The structures of organic compounds can be depicted in condensed, expanded, and three-dimensional structural formulas.

The molecular formula $C_{2} H_{6}$ identifies the composition of ethane, a gaseous hydrocarbon belonging to the paraffin series.1

While a molecular formula specifies the number and type of atoms present in a molecule, it does not describe the specific way those atoms are linked or their three-dimensional arrangement. In the case of ethane, the formula $C_{2} H_{6}$ indicates that the molecule consists of two carbon atoms and six hydrogen atoms.21

To understand the actual structure of ethane, a structural formula is required. This reveals that the two carbon atoms are bonded to each other, with each carbon atom also bonded to three hydrogen atoms. Furthermore, because carbon atoms form covalent bonds in a tetrahedral orientation, the molecule possesses a specific three-dimensional architecture that the simple molecular formula $C_{2} H_{6}$ does not explicitly convey.23