Leave the text unchanged, do not delete or add anything, just correct typos, punctuation, and paragraphing! Use [English] and use Markdown for formatting. We'll discuss three categories of exceptions to the octet rule when drawing Lewis structures. The first exception is atoms that can accommodate more than eight electrons, the second exception is molecules with an odd number of electrons, and the third exception is atoms that are satisfied with fewer than eight valence electrons. Some Lewis structures will have atoms with more than eight valence electrons, such as 10, 12, or 14 valence electrons associated with a single atom. This is an expanded octet. The atom must be in the third row or below of the periodic table to accommodate more than eight electrons. Nonmetals in the third row of the periodic table begin to have unfilled 3d subshells that can accommodate these electrons. In valence bond theory, we'll discuss using the unfilled d subshell for a process called hybridization of atomic orbitals. Other Lewis structures may have an odd number of valence electrons. When this is the case, it's not possible for every atom to have exactly eight electrons, and one electron will be unpaired. The unpaired electron makes the particle a free radical. Free radicals are generally highly reactive because of their unpaired electron. Let's draw the Lewis structure for nitrogen dioxide as an example. Nitrogen dioxide has 17 valence electrons. We can draw the Lewis structure first with just single bonds. Nitrogen is the central atom, and the two oxygen atoms are peripheral atoms. We've now used up four of the valence electrons and have 13 valence electrons remaining. We'll then satisfy the octet rule for our peripheral oxygen atoms. Each oxygen atom wants an additional six electrons. Now we've used up 16 electrons. Our last electron can go on nitrogen, our central atom; nitrogen now has five electrons. Although we cannot give nitrogen eight electrons, we could create one double bond using a lone pair of electrons on oxygen so that nitrogen will have seven valence electrons. Since we could've also created the double bond with the oxygen on the left, we can draw our other resonance structure as well. The unpaired electron on nitrogen makes nitrogen dioxide a free radical. Some atoms in Lewis structures are satisfied with fewer than eight electrons. For example, boron can be satisfied with just six valence electrons. In the Lewis structure for boron trifluoride, boron has a single bond with each of the three fluorine atoms. Although we may think we could create a double bond with one of the fluorine atoms using a lone pair of electrons on fluorine, boron is satisfied with just six electrons instead of eight. Beryllium is satisfied with just four electrons. In BeH2, for example, there are only a total of four valence electrons, and these go to create our two single bonds. Generally, compounds with incomplete octets are also more reactive.