Electron Configurations and Electronic Diagrams

Carbon has six electrons, two in the Is orbital, and four valence electrons that occupy the 2s and 2p valence orbitals. Based on the rules briefly reviewed here, the lowest energy electronic diagram of the valence shell of carbon is as shown in the margin. 

The familiar octet rule, which states that atoms are most stable when their valence shell is full, suggests that carbon in a molecule will take on four more electrons from other atoms so as to possess an octet of electrons and thereby attain a noble gas configuration. The number of bonds that an atom can make is called its valence number. If each bond that carbon makes is created by the donation of a single electron from an adjacent atom s atomic orbitals, carbon will make four bonds. Carbon is said to have a valence of four. This valence is by far the most common bonding arrangement for C. When carbon has fewer than four bonds it is in a reactive form, namely a carbocation, radical, carbanion, or carbene. When a similar analysis is done for N, O, and F, it is found that these atoms prefer three, two, and one bond(s), respectively. 

---