Octet rule chemical formula

Lewis structure (Section 1 3) A chemical formula in which electrons are represented by dots Two dots (or a line) be tween two atoms represent a covalent bond in a Lewis structure Unshared electrons are explicitly shown and sta ble Lewis structures are those in which the octet rule is sat isfied... 

When more than one structural formula for a given chemical species can be written in agreement with the octet rule, this usually means that resonance must be considered to describe the real structure adequately. The benzene molecule and the carbonate ion, CO, are well-known examples ... 

The bond orders we are considering are the ones defined in terms of the classical structural formulae, which can be related to the numbers of bonding and anti-bonding electrons. They are not the bond orders derived from molecular orbital numerical calculations as given by Eq. (9.45). An additional uniformity involving such bond orders and chemical equations can be found, directly related to the octet rule. For example, by considering... 

Barker [18] additionally comments, that teachers put far too much emphasis on the Octet rule in order to determine formulas and bindings of chemical species. As a result, the students rely on this rule to deduce formulae. During the lesson unit on ionic bonding, teachers often use this rule, in order to show that some atoms fill their shells through electron transfer instead of sharing electrons in covalent bonding. She further points out, that students are not capable of understanding how ion lattices are formed solely based on this explanation [18]. 

Ionisation of atomised metal may seem an extreme case, so perhaps it is not important if students think of the Na+ ion as more stable than the atom. However students have a strong tendency to see any species with an octet of electrons as stable, and research shows that by the end of secondary education, students will commonly rate a whole range of dubious ions as more stable than atoms because they have foil shells or octets of electrons. So not only do students tend to think Na is a stable ion, they make the same judgement about the chemically quite ridiculous species Na shown in Figure 3.7. It is important, therefore, that teachers make sure that students do not over-generalise the octet rule from a very useful rule of thumb for identifying the most likely formulae for molecules and ions, and adopt it as an absolute principle to judge stability and explain why reactions occur. 

In earlier sections of this chapter, it was shown how the chemical formulas of some compounds follow logically from the sharing or exchange of electrons in accordance with the octet rule. However, long before the nature of atoms or the existence of electrons was known, accurate chemical formulas were written for many common compounds. In this section, it is shown how chemical formulas are calculated from laboratory data. 

Lewis summarized much of his theory of chemical bonding with the octet rule. According to the octet rule, atoms will lose, gain, or share electrons in order to achieve a noble gas electron configuration. This rule enables us to predict many of the formulas for compounds consisting of specific elements. The octet rule holds for nearly all the compounds made up of second period elements and is therefore especially important in the smdy of organic compounds, which contain mostly C, N, and O atoms. 

---