Question 3.11: Covalent Bonding of Carbon Why does carbon have four bonds a...
Covalent Bonding of Carbon
Why does carbon have four bonds and no unshared pairs of electrons in some covalent compounds?
Strategy
In answering this question, you need to consider the electron configuration of carbon, the number of electrons its valence shell can hold, and the orbitals available to it for sharing electrons to form covalent bonds.
In forming covalent compounds, carbon reacts to obtain a filled valence shell; that is, a complete octet in its valence shell and an electron configuration resembling that of neon, the noble gas nearest it in atomic number.
Carbon is a second-period element and can contain no more than eight electrons in its valence shell; that is, in its one 2s and three 2p orbitals. When carbon has four bonds, it has a complete valence shell and a complete octet. With eight electrons, its 2s and 2p orbitals are now completely occupied and can hold no more electrons. Adding an additional pair of electrons would place ten electrons in the valence shell of carbon and violate the octet rule.
■ Quick Check 3.11
Draw a Lewis structure of a covalent compound in which carbon has:
(a) Four single bonds (b) Two single bonds and one double bond
(c) Two double bonds (d) One single bond and one triple bond