To summarize, Lewis structures show, in a simple graphical form, the number and type of bonds in a molecule (connectivity), as well as the number of unshared electron pairs, or unpaired electrons. Regardless of how the electrons are drawn, they all show that oxygen has two unshared electron pairs and forms a double bond with carbon, nitrogen has only one unshared electron pair, and chlorine has three. The following figure shows different forms of Lewis representation for the ClCCONH 2 molecule. In other texts such representations appear with lines only. In addition, to further simplify the structures, instead of dots, lines ( –) are drawn to represent bonds and dots for non-bonding electrons (non-bonding electrons). Alternatively, the electrons can be represented with the symbols to visualize more clearly their « origin «. It is still considered one of the most famous forms of structure and representation of organic molecules.įor example, in the figure above, hydrogen, carbon, nitrogen, oxygen and fluorine atoms are depicted with their valence electrons (1, 4, 5, 5, 6 and 7, respectively), as well as Lewis structures for CH 3F (fluoromethane) and HCONH 2(formamide) molecules. Lewis developed a representation system where valence electrons are indicated around atoms with dots ( –) and a pair of electrons with a colon ( :). This electronic configuration is particularly stable and similar to that of a noble gas.
However, since carbon has 4 valence electrons, it will need to complete the 4 valence ( s, p x, p y, p z) orbitals with 4 additional electrons, to reach a total of 8 valence electrons ( octet rule). Hydrogen, with 1 electron in an s orbital, needs only 1 electron to complete its valence shell.
Gilbert Newton Lewis proposed that for a molecule to be stable its valence shell should be complete.
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