Chemical formulas line-angle formula

In these line-angle formulas it is understood that there is a carbon atom at each vertex of the hexagon hydrogen atoms are not shown. This model is consistent with many of the properties of benzene. The molecule is a planar hexagon with bond angles of 120°. The hybridization of each carbon is sp2. However, this structure is misleading in one respect Chemically, benzene does not behave as if double bonds were present... 

Line-angle formulas are shorthand representations of organic molecules in which bond lines are drawn, but chemical symbols are written only for elements other than carbon and hydrogen. 

Fig. 14-1 Standard 3 x 5 in. JCPDS diffraction data card (card 628 from Set 5) for sodium chloride. Appearing on the card are 1 (file number), 2 (three strongest lines), 3 (lowest-angle line), 4 (chemical formula and name of substance), 5 (data on diffraction method used), 6 (crystallographic data), 7 (optical and other data), 8 (data on specimen), and 9 (diffraction pattern). Intensities are expressed as percentages of Ii, the intensity of the strongest line on the pattern. Most cards have a symbol in the upper right comer indicating the quality of the data (high quality), i (lines indexed, intensities fairly reliable), c (calculated pattern), and o (low reliability). (Courtesy of Joint Conunittee on Powder Diffraction Standards.)...

For the differentials of Equations (3.22) through (3.26), n is held constant. The omission of n from the parentheses subscripts is a frequent practice. This is analogous to the omission of carbon and hydrogen atom symbols from chemical formula diagrams of the line-angle variety the experienced viewer infers their presence. It is important that Cy, Cp, Op, Pj-, and p apply to closed systems. They are all positive for stable systems—the type under the lens of this chapter. 

In the preceding simplified structural formula for benzene the six hydrogen atoms have been omitted. Resonance between the two possible arrangements of the three double bonds1 is indicated by the circle. Chemical shorthand of the following type is used throughout the book. Carbon atoms may be represented by an angle or the end of a line, but other atoms will always be shown. 

---