This lesson continues the series on organic chemistry, focusing on alkenes and their general formula, (CnH_{2n}), which reflects their unsaturated nature due to the presence of carbon-to-carbon double bonds. The instructor explains the naming conventions for alkenes, emphasizing that while ethene and propene do not require position numbers for their double bonds, compounds like but-1-ene and pent-1-ene do, to indicate the location of the double bond along the carbon chain. The lesson outlines the distinction between saturated hydrocarbons (alkanes) with single bonds and unsaturated hydrocarbons (alkenes) with double bonds, highlighting that methane cannot exist due to the nature of hydrogen’s bonding capabilities.