By which unit do the successive members of the homogenous series CH$$_4$$​, C$$_2$$​H$$_6$$​, and C$$_3$$​H$$_8$$​differ from each other?

Correct option is D

• Methane (CH₄) is the first member of the series.

• Ethane (C₂H₆) is formed by adding one CH₂ unit to methane.

• Propane (C₃H₈) is formed by adding another CH₂ unit to ethane.

• Alkanes follow the general formula CₙH₂ₙ₊₂, and this pattern of increasing by CH₂ is consistent across the series.

• Alkanes are saturated hydrocarbons, meaning they contain only single bonds between carbon atoms.

• The differences in molecular structure between members of a homologous series lead to differences in physical properties such as boiling points and melting points.

• CH₂ is the simplest structural unit in this case, used in the construction of larger molecules in the series.

Additional Information:

• CH₃: This is the methyl group, which is the unit by which successive members of the homologous series of alkanes (like CH₄, C₂H₆, C₃H₈) differ. Each member of the series differs by one CH₃ group.

• CH: This would refer to a methylene group, but it is not the unit by which successive alkanes differ. Instead, CH₂ groups are often seen in alkenes and other unsaturated hydrocarbons.

• CH₄: This is methane, the simplest alkane, and does not represent the unit by which other alkanes differ in the homologous series.