Editing Structural formula (section)

== Structures in structural formulas ==

=== Bonds ===
[[Chemical bond|Bonds]] are often shown as a line that connects one atom to another. One line indicates a [[single bond]]. Two lines indicate a [[double bond]], and three lines indicate a [[triple bond]]. In some structures the atoms in between each bond are specified and shown. However, in some structures, the carbon molecules are not written out specifically. Instead, these carbons are indicated by a corner that forms when two lines connect. Additionally, Hydrogen atoms are implied and not usually drawn out. These can be inferred based on how many other atoms the carbon is attached to. For example, if Carbon A is attached to one other Carbon B, Carbon A will have three hydrogens in order to fill its octet.<ref name=":0">{{Cite book |last=Brown |first=William Henry |title=Organic chemistry |date=2018 |author2=Brent L. Iverson |author3=Eric V. Anslyn |author4=Christopher S. Foote |isbn=978-1-305-58035-0 |edition=Eighth |location=Boston |oclc=974377227}}</ref>
[[File:Bonds and Electron Sharing.jpg|left|thumb|409x409px|This shows the bonds in relation to the electrons being shared.]]
[[File:Connection of Bonds.jpg|none|thumb|401x401px|This shows how bonds are depicted to connect to other atoms in the various structural formulas used.]]

=== Electrons ===
[[File:Ions.svg|thumb|298x298px|Charges on atoms and their formation]]
[[Electrons]] are usually shown as colored-in circles. One circle indicates one electron. Two circles indicate a pair of electrons. Typically, a pair of electrons will also indicate a negative charge. By using the colored circles, the number of electrons in the valence shell of each respective atom is indicated, providing further descriptive information regarding the reactive capacity of that atom in the molecule.<ref name=":0" />

=== Charges ===
Oftentimes, atoms will have a positive or negative [[Electric charge|charge]] as their octet may not be complete. If the atom is missing a pair of electrons or has a proton, it will have a positive charge. If the atom has electrons that are not bonded to another atom, there will be a negative charge. In structural formulas, the positive charge is indicated by ⊕ , and the negative charge is indicated by '''⊖ .'''<ref name=":0" />
[[File:Absolute configuration.svg|thumb|275x275px|This image shows the wedges in the structural formula and how they indicate the stereochemistry of the compound.|none]]

=== Stereochemistry (Skeletal formula) ===
[[File:Strychnine.svg|thumb|200px|Skeletal formula of [[strychnine]]. A solid wedged bond seen for example at the nitrogen (N) at top indicates a bond pointing above-the-plane, while a dashed wedged bond seen for example at the hydrogen (H) at bottom indicates a below-the-plane bond.]] [[Chirality (chemistry)|Chirality]] in skeletal formulas is indicated by the [[Natta projection]] method. [[Stereochemistry]] is used to show the relative spatial arrangement of atoms in a molecule. Wedges are used to show this, and there are two types: dashed and filled. A filled wedge indicates that the atom is in the front of the molecule; it is pointing above the plane of the paper towards the front. A dashed wedge indicates that the atom is behind the molecule; it is pointing below the plane of the paper. When a straight, un-dashed line  is used, the atom is in the plane of the paper. This spatial arrangement provides an idea of the molecule in a 3-dimensional space and there are constraints as to how the spatial arrangements can be arranged.<ref name=":0" />

=== Unspecified stereochemistry ===
[[File:Skeletal Structure of Cyclic D-Fructose.svg|thumb|left|175px|[[Fructose]], with a bond at the [[hydroxyl]] (OH) group upper left of image with unknown or unspecified stereochemistry]]
Wavy single bonds represent unknown or unspecified stereochemistry or a mixture of isomers. For example, the adjacent diagram shows the [[fructose]] molecule with a wavy bond to the {{chem2|HOCH2\s}} group at the left. In this case the two possible ring structures are in chemical equilibrium with each other and also with the open-chain structure. The ring automatically opens and closes, sometimes closing with one stereochemistry and sometimes with the other.{{cn|date=January 2025}}

Skeletal formulas can depict [[cis-trans isomerism|''cis'' and ''trans'' isomers]] of alkenes. Wavy single bonds are the standard way to represent unknown or unspecified stereochemistry or a mixture of isomers (as with tetrahedral stereocenters). A crossed double-bond has been used sometimes, but is no longer considered an acceptable style for general use.<ref name="IUPAC-2006">{{cite journal |author=J. Brecher |year=2006 |title=Graphical representation of stereochemical configuration (IUPAC Recommendations 2006) |url=http://www.iupac.org/publications/pac/pdf/2006/pdf/7810x1897.pdf |journal=[[Pure and Applied Chemistry|Pure Appl. Chem.]] |volume=78 |issue=10 |pages=1897–1970 |doi=10.1351/pac200678101897 |s2cid=97528124}}</ref>

[[File:E-Z notation in alkenes.svg|thumb|400px|center|Alkene stereochemistry]]