*Only Carbon and Silicon can form bonds as nonmetals from this group *Silicon and Germanium are the only semi-metals in this group *Tin and Lead are definitely metals because of how they loose electrons because of the distance from the nucleus
Some places you will find these elements in the real world is Silicon in computer chips and solar cells. Silicon dioxide is the major component in glass. Lead is used in plumbing. And Aluminum has replaced a lot of the more expensive tin.
Germanium is used in many different products, such as it is used in many electronics and solar applications. It is transparent so it can and is used in the making of lenses and windows. It also is used in x-ray machines.
Almost twenty years before germanium was found, Dmitri Mendeleev predicted it's existence. It was discovered by a German chemist named Clemens Winkler in 1886.