Atom Labels

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A simple atom label may contain any of the following:

	A single element.
	An element and some number of hydrogen atoms.
	A nickname.
	Repeating units within parentheses.
	A series of any combination of the above.

When analyzing an atom label, ChemDraw starts at the left and continues to the right, applying standard rules of valence to determine which atoms are bound to which. The exception is with an atom label in Automatic alignment on the left side of a compound. This sort of atom label is displayed "backwards" (H₃CO instead OCH₃) and is therefore parsed from right to left. Standard valences for each atom are defined in the Isotopes Table.

By definition, a "simple" atom label has all bonds attached to the first (or last) character. A multi-attached atom label has bonds connected to more than one character, or has all of its bonds attached to a specific character in the middle of the atom label. Multi-attached atom labels are always parsed from beginning to end, but again the beginning might be on the right if the atom label was in Automatic style and on the left side of the original structure:

	A multi-attached label that is parsed from left to right.
	A multi-attached label that is parsed from right to left.
	A bond attached to the open parenthesis of a repeating group is treated as if bonded to the first of those groups.
	A bond attached to the close parenthesis or repeat count of a repeating group is treated as if bonded to the last of those groups.

Multiple fragments within a single label can be specified in the following ways:

	Implicitly, using standard valence rules.
	Explicitly, using a space, period (unsuperscripted or unsubscripted), bullet, or combination.
	An unsuperscripted, unsubscripted integer at the start of a fragment is recognized as a stoichiometric multiplier and is treated as if the appropriate number of fragments were drawn explicitly.