What is the molecular formula of the first alkene ethene?

Ethene, also known as ethylene, is the simplest alkene and has the molecular formula C₂H₄. This means it consists of two carbon atoms and four hydrogen atoms.

Alkenes are characterized by the presence of at least one carbon-carbon double bond. For ethene, the double bond occurs between the two carbon atoms, which is consistent with the alkene family. The general formula for alkenes can be represented as CₙH₂ₙ, where "n" is the number of carbon atoms. In the case of ethene, with "n" equal to 2, this gives us C₂H₄.

The other molecular formulas do not accurately represent ethene. For example, C₁H₂ refers to a compound with only one carbon atom, which does not fit the definition of ethene as it requires two carbon atoms. C₂H₆ represents ethane, an alkane that has single bonds only, and C₃H₆ represents propene, the next alkene in the series with three carbon atoms. Therefore, C₂H₄ is the precise molecular formula for ethene.