Lesson 2 of 13 · 7 min
Structural representations
NCERT § "Structural Representations of Organic Compounds"
The label on Riya's vinegar bottle says 'acetic acid'. Her chemistry teacher might write CH₃COOH, draw every bond, or sketch just two short lines and an OH. All of them describe the same molecule.
The lesson in notes
In short
A complete (Lewis or dash) structural formula shows every bond as a dash and may show lone pairs.
A condensed formula omits some or all dashes and groups identical units, for example CH₃(CH₂)₆CH₃.
In bond-line formulas carbon and hydrogen atoms are not written; each line end or bend is a carbon, and hydrogens are assumed to fill each carbon's valence.
Heteroatoms such as O, N and Cl, and the hydrogens on them, are always written explicitly in bond-line formulas.
Three-dimensional structures are drawn with solid wedges for bonds coming towards the viewer, dashed wedges for bonds going away, and plain lines for bonds in the plane of the paper.