chem..semi-metal form compound既問題..

Generally,

semi metal + non metal usually give covalent compounds, for example,

Silicon hydrides are simple discrete molecules. (no of Si cannot more than 11)

Germanium hydrides are simple discrete molecules too.

More examples

Pure Si, Ge are giant covalent network with a diamond structure.

Silicon(IV) oxide is giant covalent network (quartz)

Germanium(IV) oxide is ionic or giant covalent, depends on its structure. (ionic if rutile, covalent if quartz)

Structure of Silicon(II) oxide is unknown.(because it is highly unstable)

Germanium(II) oxide is ionic.