According to Huckel?s rule for aromaticity, planar monocyclic rings containing $(4n + 2)n$ electrons (where $n = 0, 1,2,3$ and so on) should be aromatic. Another requirement for aromaticity is planarity of the ring. In the given compounds, all contains $6n$ electrons, therefore for them, $n$ comes out be $1$,hence, pyrrole, thiophene and furan are all aromatic.
Hydrocarbons can be described asorganic compounds that consists only hydrogen and carbon atoms. These compounds are of different types and thereby have distinct natures. Hydrocarbons are colorless gases and are known for discharging faint odours. These have been categorized under four major classes named as alkynes,alkanes, alkenes, and aromatic hydrocarbons.
Types of Hydrocarbons
Saturated hydrocarbons - Saturated hydrocarbons are those compounds where there is a single bond exists between carbon atoms and are saturated with atoms of hydrogen.
Unsaturated hydrocarbons - Hydrocarbons comprises of at least one double or triple bond between carbon atoms are known as unsaturated hydrocarbons.
Aliphatic hydrocarbons - The term denotes the hydrocarbons formed as an outcome of the chemical degradation of fats.Aliphatic hydrocarbons are basically chemical compounds.
Aromatic hydrocarbons - They are distinguished because of the presence of benzene rings in them. They give away distinct types of aroma. These hydrocarbons comprises of only hydrogen and carbon atoms.
