Organic functionalization of the semiconductor (100) surfaces of C, Si and Ge using traditional organic reactions has been attracting tremendous interest in the past decade, which has developed as a very hot and interesting topic at the border between material science and synthetic organic chemistry. In this review, we will give a brief summary of our recent research work in this regard. It is well demonstrated that, due to the structural similarity of the surface dimer of X (100) (X=C, Si and Ge) to alkenes, many well-known reactions associated with alkenes, such as carbenes addition reaction and Diels-Alder reaction, have been used to modify the (100) surface of C, Si and Ge successfully. In particular, a joint combination of theory and experiment empowers us to gain quick insight into the microscopic mechanism of chemistry of functionalization of the (100) surface of C, Si and Ge by synthetic organic reactions. All of these strongly advance the mantra of chemistry, i.e. similar structure dictates analogous function. In other words, fullerenes, carbon nanotubes and the (100) surface of X (100) all have an analogous bonding motif similar to alkenes, hence suggesting that similar chemistry is able to exist among them.