3.1: Introduction to Bonding

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Learning Objectives

Define bond.
State the octet rule.

As stated in the previous chapter, valence electrons are solely-responsible for determining how elements interact with one another. Electrons are most stable when they exist in pairs. Electron dot structures, which were discussed in the previous chapter, visually represent an atom's valence electrons as dots that are written around an elemental symbol. If two electrons are written on the same side of the electron dot structure, they are considered paired electrons. Therefore, an unpaired electron must exist alone on a particular side of an electron dot structure. An electron dot structure for sulfur, which contains both paired and unpaired electrons, is shown below in Figure \(\PageIndex{1}\).

Sulfur 6 Dot - Single Structure.png — Figure \(\PageIndex{1}\): A valid electron dot structure for sulfur.

The noble gases, which include helium, He, neon, Ne, argon, Ar, krypton, Kr, xenon, Xe, and radon, Rn, are the only elements that naturally possess fully-paired electrons. These elements are found in Group 8A on the periodic table and, therefore, have 8 valence electrons. The electron dot structure for neon, which is shown below in Figure \(\PageIndex{2}\), illustrates that all eight of neon's valence electrons exist in pairs. Recall from Chapter 2 that the elements in Group 18, or Group 8A, were given the "Descriptive Name" of the noble gases because they do not readily bond with other elements and were likened to royals and nobles, who did not often voluntarily interact with "commoners." This inactivity can now be explained by the fully-paired and, therefore, highly-stable, valence electron configuration of these elements. Because the noble gases naturally possess fully-paired valence electrons, they are inherently stable and, consequently, exist as monatomic, or single-atom, "compounds."

Neon Electron Dot Structure.png — Figure \(\PageIndex{2}\): Neon's electron dot structure.

The noble gases are unique in that they are the only elements to naturally possess an octet, or eight, fully-paired valence electrons. The elements that exist in all of the other columns on the periodic table cannot naturally achieve an octet configuration, as they do not possess eight valence electrons. As a result, these elements are not stable by themselves, and instead must form bonds, or lasting associations between atoms or ions that result in the formation of compounds, with other elements to achieve stable valence electron configurations. Atoms can bond through either ionic or covalent interactions, as will be discussed in the remaining sections of this chapter.