Ethene is the simplest alkene compound. Ethene has two carbon atoms and four hydrogen atoms and its molecular formula is C2H4.
Alkene compounds include double bond or bonds between carbon atoms. Therefore at least there should be two carbon atoms to make an alkene compound.
Due to requirement of a double bond, at least two carbon atoms are required to complete the alkene. So n=2 is the first value we can substitute the general equation of alkenes.
Simplest alkene, ethene is symmetric. But, propene is not symmetric. So there is no problem in addition reactions in ethene to decide whether atoms are added.
As an example, we can take ethene and HBr reaction. H and Br atoms can be added to any carbon of the ethene molecule.
But, reaction of propene with HBr, give products in different way. There H of HBr is added to the carbon atom which have higher number of hydrogen atoms. Br is combined with other carbon atom.
Yes. Ethene, simplest alkene is a gas. First alkenes series are gases. Ethene molar mass is 28 g mol-1.