Group 4 elements form mostly covalent compounds because of
state of the external energy level s2p2 that leads to border values of ionization energy (energy required to remove an electron) and electronegativity power. In the periodic system, they occupy an intermediate position between non-metals, whose atoms in reactions are easier to attach than they give, electrons, and metals that easily give away valence electrons. It is therefore necessary to expect that the carbon and silicon atoms will not fully release or capture valence electrons during chemical reactions, but will form covalent bonds. Indeed, the four valence electrons of the atoms of these elements usually form four covalent bonds with other atoms. In the vast majority of their compounds, carbon and silicon are tetravalent.