Hello Dear,

CH3CH2 can also be written as C2H5, which is the second member of the series called Alkyl group as carbon molecule content is 2. So, this molecule (CH3CH2) is called ETHYL. This is the ethyl group, which occurs in several organic compounds, like ethanol (CH3-CH2-OH). Remember, the ethyl group cannot exist independently, as the tetravalency of the Carbon Atom will not be satisfied.

A better way of expressing this is CH3-CH2-R

Good Luck