Name | Molecular Formula | Structural Formula | Konnectivity Formula* | Stereochemical Formula |
---|---|---|---|---|
Methane |
CH4 |
CH4 |
||
Ethanol |
C2H6O |
CH3CH2OH |
||
Diethyl ether |
C2H6O |
CH3OCH3 |
Nomenclature
Chapter 2
Audio created by Google NotebookLM. Note: I have not verified the accuracy of the audio or transcript. Download the transcript here (created by Restream).
IUPAC (International Union of Pure and Applied Chemistry; founded 1919), “is the world authority on digital standards in chemistry; chemical nomenclature and terminology, including the naming of new elements in the periodic table; on standardized methods for measurement; and on atomic weights.” IUPAC nomenclature is a method of naming chemical compounds.
- Overall summary of chemical nomenclature (PDF)1
- Inorganic compounds (the Red Book; PDF)2
- Organic compounds (the Blue Book; PDF)3
- Polymers (the Purple Book; PDF)4
Molecular models
Molecules can be represented in various ways.
*See the K? Should be C right? “Connectivity”. So why the K? Because if I put in a C, the code throws an error when building the table. It’s a bug in one of these packages. Not sure which…
Skeletal formulas and molecular models
Click the dropdowns to see the skeletal formulas (line structures) and molecular models for the structures in the table above.
Methane
Ethanol
Dimethyl ether
- Molecular formulae for compounds consisting of discrete molecules are formulae that describe the composition of the molecule where each element is grouped and the number of each atom of an element type is indicated with a subscript.
- Structural formulae give information about how certain atoms are grouped together in the molecule.
- Connectivity formulae give information about the way atoms in a molecule or ion are connected and arranged in space. Lone electron pairs are typically omitted but can be shown as seen here.
- Stereochemical formulae represents the structure in three dimensions. Lone electron pairs are typically omitted but can be shown as seen here.
- Molecular models are visualization schemes for visualizing structures in three dimensions. Commonly, ball-and-stick models are used (as seen above in the dropdowns) but a variety of others exist.
Covalent Compounds
Naming covalent (molecular) compounds follow a set of rules that are different than ionic compounds.
Homogeneous polyatomic
Molecules made up of one type of element are called by their element name.
Formula | Name |
---|---|
H2 |
hydrogen |
N2 |
nitrogen |
O2 |
oxygen |
F2 |
fluorine |
Cl2 |
chlorine |
Br2 |
bromine |
I2 |
iodine |
P4 |
phosphorous |
S8 |
sulfur |
Compounds with common names
Some molecular compounds are well-known by their common names and are not referred to by their IUPAC names.
Binary Compounds
Most binary compounds are combinations of two nonmetal elements from Groups 14-17 with one another or with hydrogen. Elements are listed in the order of increasing group order. If two elements are in the same group, the element in the largest period is usually written first.
Binary molecular compounds are arranged in the (reverse) order given in Figure 1. That is, the first encountered element is typically preceded by the second encountered element (bottom-left first and top-right last). Hydrogen is a weird exception.

Hydrogen can form binary compounds with all nonmetals except for the noble gases. Hydrogen is usually written first when in compounds containing oxygen, sulfur, and the halogens. The other nonmetal is named by adding -ide to the stem of the name.
Naming Rules:
- The first part of the name is hydrogen if the first element listed is hydrogen
- The second part is the root element name followed by -ide
Multiplicative prefixes
Multiplicative prefixes are numerical multipliers in IUPAC nomenclature that indicates the number of particular atoms or functional groups that are in a molecule. These are used when naming most other binary compounds.
Naming binary compounds if molecular:
- Element name of nonmetal. Omit “mono” for first element
- Root element name of second nonmetal with -ide ending
- No prefix if first element is hydrogen
- Drop the second “o” in “mono” prior to a vowel
- Drop the “a” in prefixes ending in “a” prior to a vowel
Ions
A monatomic ion is a charged particle made up of a single atom. They are named after their element followed by their charge in parenthesis. Monatomic anions are also named after their root element name followed by -ide.
Figure 2 shows the typical charge(s) some elements adopt when becoming an ion.
The following transition metals are said to be (for this class) invariant, that is, they only adopt one charge.
- Cd2+
- Zn2+
- Ag+
Polyatomic ions
A polyatomic ion is a molecular ion with a non-zero charge containing two or more covalently bound atoms or of a metal complex, that can behave as a single unit (Table 7).
Anions: Group 12 | |
---|---|
Cations: Group 15 | |
Cations: Group 16 | |
Anions: Group 14 | |
Anions: Group 15 | |
Anions: Group 16 | |
Transition metals | |
Oxyanions
Most polyatomic ions are oxyanions (or oxoanions), conjugate bases of oxyacids. For example, the phosphate anion, PO43–, is an oxyanion that is a conjugate base of the parent H3PO4 molecule (phoshporic acid). The suffixes ‘-ide’, ‘-ite’, ‘-ate’, and prefixes ‘hypo-’ and ‘per-’ are used in a systematic fashion depending on the number of oxygen atoms present.
The order of these pre/suffixes from least to most oxygens present is as follows:
Table 8 illustrate these naming schemes.
Anions: Group 15 | |
---|---|
Anions: Group 16 | |
Anions: Group 17 | |
Binary Ionic Compounds
Ionic compounds form between cations and anions about an ionic bond. Naming ionic compounds depend on the types of charged particles in the compound. These particles can be
- Metals of one charge (invariant)
- non-transition metals
- Cd, Ag, Zn (treated as invariant for this class)
- Metals that can adopt various charges (multivalent)
- most transition metals
- Non-metals
- Polyatomic Ions
The charge of the multivalent metal can be deduced by considering the charge of the other particle and the charge on the overall compound. For example, the charge on iron in FeCl2 is 2+ because each chlorine atom adopts a 1– charge giving a neutral ionic compound.
Invariant metal + nonmetal
Naming rules:
- Elemental name of metal
- Elemental root name of nonmetal with “ide” ending
Remember that Cd, Zn, and Ag are considered to be invariant (for this class) and adopt the following charges:
- Cd2+
- Zn2+
- Ag+
Invariant metal + polyatomic ion
Naming rules:
- Elemental name of metal
- Name of polyatomic ion (see Table 7)
Multivalent metal + nonmetal
Naming rules:
- Elemental name of transition metal
- Use Roman numerals in parenthesis immediately following transition metal name (no space) to define the oxidation state (which is equal to the charge on the metal)
- Elemental root name of nonmetal with “ide” ending
Multivalent metal + polyatomic ion
Naming rules:
- Elemental name of metal
- Use Roman numerals in parenthesis immediately following transition metal name (no space) to define the oxidation state (which is equal to the charge on the metal)
- Name of polyatomic ion (see Table 7)
Polyatomic ion + nonmetal
Naming rules:
- Name the element or polyatomic ion (whichever comes first)
- Name the element or polyatomic ion (whichever comes second). If the second particle is an element, write out the root name of the element and end it with -ide.
Polyatomic ion + polyatomic ion
Naming rules:
- Name the first polyatomic ion
- Name the second polyatomic ion
Hydrates
Hydrates are substances that contain water. Hydrated ionic compounds are ionic compounds that contain water. If hydrate ionic compounds are dried, they are referred to as being anhydrous.
Naming rules:
- Name the ionic compound first following the rules for naming ionic compounds
- Name the number of waters by using the appropriate multiplicative prefix (Table 4) conjoined with the word “hydrate”
Note that chemical formulas for hydrates contain a center/middle dot that separate the compound from the waters.
Simple Organic Compounds
Organic compounds are defined in a couple different of ways:
- compounds that contain a carbon-hydrogen or carbon-carbon (e.g. CH4)
- any chemical compound that contains carbon (e.g. CCl4, CN–, HCN, and CO2)
Hydrocarbons are molecules consisting of only carbon and hydrogen.
Alkanes
Alkanes are acyclic saturated hydrocarbons (each carbon forms four single bonds with other carbon or hydrogen atoms). Alkanes can exist as structural isomers, more than one compound with the same chemical formula but existing with a different arrangement of bonds.
Structural Isomers of C5H12
Pentane
Isopentane
Neopentane
Prefixes are used depending on the number of carbon atoms present (Table 16).
Alkanes containing a single chain of saturated carbon atoms (where each carbon forms four single bonds) without any branching (referred to as linear) are named by first using the appropriate prefix followed by “ane”. Sometimes, ‘n-’ (for normal) is included at the front of the name for these molecules but can be omitted.
Alcohols
Alcohols are organic compounds that contain at least one hydroxyl (–OH) functional group. The simplest alcohols are similar to alkanes in structure and in naming. Use the appropriate prefix (Table 16) associated with the number of carbon atoms followed by “anol” as the suffix. The leading “1-” can be excluded.
Carboxylic acids
Carboxylic acids are organic compounds that contain at a carboxyl group (–COOH or –C(=O)–OH) functional group. Naming of straight chain carboxylic acids is similar to naming alkanes. Use the appropriate prefix (Table 16) associated with the number of carbon atoms followed by “anoic” as the suffix and terminate the name with the word “acid”.
Acids and Bases
Below is a table of common strong and weak acids and bases. Note that many acids exist naturally as a gas (e.g. HCl(g) is hydrogen chloride). Sometimes, if the substance is dissolved in a solvent (such as water), and meets the definition of an acid, only then is it called an acid (e.g. HCl(aq) is hydrochloric acid). Exceptions include organic compounds such as carboxylic acids (e.g. acetic acid) which are still referred to as their acid name even in the absence of water. Anhydrous acetic acid is also called “glacial acetic acid”.
Strong Acid | |
---|---|
Weak Acid | |
Strong Base | |
Weak Base | |