Explain why carbon forms compounds mainly by covalent bond.
Carbon has 4 electrons in its outermost shell and requires 4 more electrons to attain a noble gas electronic configuration. It cannot form a C4+ ion, as the removal of 4 valence electrons requires a huge amount of energy. The C4+ ion thus formed will have 6 protons and 2 electrons, which will make it highly unstable. Carbon cannot form a C4− ion, as its nucleus with 6 protons cannot hold 10 electrons due to inter electronic repulsion. So, carbon achieves a noble gas electronic configuration only by sharing its 4 valence electrons with other elements. Thus, it forms compounds mainly by covalent bonds.