Here's a video discussion of some chemical nomenclature (11min): CrashCourse Chemistry: How To Speak Chemistrian, on YouTube
Want to learn and practice nomenclature in a more interactive way? Check out my new project, Chemiatria!
Chemical nomenclature is the names we use for chemicals. For instance, H2O is called "water", and CH4 (the gas you burn in a stove) is called "methane". You should learn the chemical nomenclature here on this page now, so that you will be able to understand when it is used.
Here is some important info about how we write chemicals.
There are lots of elements and you don't need to memorize them all. Here are a few that you should learn right now, though, because they are common or important, so that you won't be confused when they are mentioned later. They are organized by their type.
Cation is another word for positive ion. The common positive ions are the ions of the alkali and alkaline earth metals and ammonium, NH4+. The alkali metals form +1 cations, such as Na+ and K+. The alkaline earth metals form +2 cations, such as Ca2+ and Mg2+. The hydrogen ion, H+ is a very common cation. For these cations, you can call them "[element name] ion", such as sodium ion or calcium ion.
You'll also see transition metal cations or main group metal cations, but it is harder to predict what charge they will have, especially because some of them can have different charges, like iron, which is commonly Fe2+ or Fe3+. The charge on a transition metal cation can also be indicated using Roman numerals in parentheses, which looks like Fe(II) or Fe(III). The Roman numerals you will need to know for chemistry are:
1 | 2 | 3 | 3 | 5 | 6 | 7 | 8 | 9 | 10 |
I | II | III | IV | V | VI | VII | VIII | IX | X |
Sometimes people use special names for these ions, in which the higher charge ion is called "[name]-ic ion" and the lower charge ion is called "[name]-ous ion", such as ferrous for Fe(II) and ferric for Fe(III), or cuprous ion for Cu(I) and cupric ion for Cu(II). I think this is most common for Fe, and I've never heard anyone call nickel(II) nickelous ion, except in our textbook, because that sounds ridiculous.
Here's a list of common cations with less predictable charges: Ag+, Cu+, Cu2+, Fe2+, Hg22+, Hg2+, Pb2+, Sn2+, Al3+, Fe3+. Elements not on the list above, that you may see soon anyway: zinc(II): Zn2+, cadmium(II): Cd2+, cobalt(II): Co2+, manganese(II): Mn2+, nickel(II): Ni2+, chromium(III): Cr3+.
When do you use Roman numerals? If the cation is not an alkali metal, alkaline earth metal, Zn, or Al. All other transition metal or main group cations should have Roman numerals to indicate the charge.
Anion is another word for negative ion. Common negative ions are the halide ions, formed from the halogen elements: fluoride, F–; chloride, Cl–; bromide, Br–; and iodide, I–. As you may have noticed, the names of anions have "-ide" at the end when they are formed from elements. Other examples include oxide, O2–, sulfide, S2–, and nitride, N3–.
There are also many important polyatomic anions, which means anions that include more than one atom. These include toxic cyanide ion, CN–, common hydroxide ion, OH–, and peroxide ion, O22–. Other important anions include acetate ion (C2H3O2–), which is in vinegar, the chlorate ion (ClO3–), the perchlorate ion (ClO4–) which is often explosive, the nitrate ion (NO3–), the carbonate ion ((CO32–) found in shells, the sulfate ion (SO42–), and the phosphate ion (PO43–). All of these end in "-ate", which means that they have more oxygen. Also, notice that "per-___-ate" means more oxygen than just "-ate", as in perchlorate.
Less common but still important are some "-ite" anions, which have less oxygen, such as nitrite (NO2–), sulfite (SO32–), chlorite (ClO2–) and hypochlorite (ClO–). Notice that "hypo-___-ite" means less oxygen than just "-ite" as in hypochlorite. Sulfite and nitrite are used to preserve foods. Sulfite salts are used in wine, dried fruit and preserved radish (mu). Nitrite salts are used in preserved meats.
One more rule says that if you take an anion like carbonate or sulfate and add one hydrogen ion, then you call that "bicarbonate" (HCO3–) or "bisulfate" (HSO4–). Or you might see it called "hydrogen carbonate" or "hydrogen sulfate". Note that because we added a hydrogen ion, the charge on the bicarbonate ion is one less than the charge on the carbonate ion. Also, note that "disulfate" is S2O72–, quite different from bisulfate.
There are many other polyatomic ions, but you don't need to learn them all now. Try to remember the ones listed above and the naming patterns. For instance, I've listed 4 anions with chlorine and oxygen. You would name similar ions based on bromine or iodine the same way, such as iodate or bromite.
Ionic compounds are compounds that include at least two components, a positive ion and a negative ion. Often the positive ion is a metal element ion and the negative ion is a non-metal ion. To name an ionic compound, you usually just give the cation followed by the anion, such as "sodium chloride" or "ammonium nitrate". If the cation is the type that could have different charges, than you should say what the charge is, such as "mercury(I) iodide" or "cupric sulfate".
How do you tell if a compound is ionic? It's ionic if it starts with a metal or ammonium (NH4+). If it starts with hydrogen it is an acid, not ionic.
Acid usually means an anion combined with the hydrogen ion as the cation. For instance, HCl is a common acid, which is the hydrogen ion and the chloride anion. If the anion ends in "-ide" then usually the acid is called "hydro-___-ic acid" such as "hydrochloric acid" for HCl. You'll see this for all the "hydrohalic acids" which are H + a halogen, such as "hydrofluoric acid" or "hydroiodic acid". You might also see "hydrocyanic acid" for HCN. If the anion ends in "-ate" than you call the acid "___-ic acid", such as "sulfuric acid", which is H2SO4, or "nitric acid", HNO3. If the anion ends in "-ite" than the acid name is "___-ous acid", such as "hypochlorous acid" for HClO. Notice that earlier "-ic" and "-ous" meant more and less charge for cations, such as ferric and ferrous ions of iron. Now it also means more and less oxygen in acids.
A slight complication is that acids that exist as gases are sometimes named differently in the gas form than in the solution form. For example, hydrochloric acid or hydrosulfuric acid usually refers to HCl(aq) or H2S(aq). If you are talking about HCl(g) you would say hydrogen chloride (naming it like the covalent compound but without the prefix, see below) or hydrogen sulfide for H2S(g).
Non-metal compounds are often called covalent compounds. Here we will only learn rules for compounds that contain two elements in simple ratios. There are many other rules for more complicated situations that you might someday learn in an organic chemistry class. These binary covalent compounds are named following a different rule from ionic compounds. You will need these prefixes which indicate how many of each type of atom are present:
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
mono | di | tri | tetra | penta | hexa | hepta | octa | nona | deca |
Element name | Symbol | Atomic number | Commonly found as... |
---|---|---|---|
Hydrogen | H | 1 | H2(g), water (H2O), acid (H+(aq)) |
Helium | He | 2 | He(g), He(l) if you want to make things very cold |
Lithium | Li | 3 | Li+ always, (aq) or in solids with anions, lithium metal Li(s) only in chem class |
Carbon | C | 6 | covalent compounds, making 4 bonds |
Nitrogen | N | 7 | N2(g) in air, in ammonia (NH3(g or l)), in basic covalent compounds, in proteins |
Oxygen | O | 8 | O2(g) in air, in water, in rock and glass, usually combined with Si |
Fluorine | F | 9 | F–(aq) or with cations in rock, in covalent compounds with carbon (non-stick pans) |
Sodium (Natrium) | Na | 11 | Na+(aq) or with anions in salts, sodium metal (Na(s)) only in chem class |
Magnesium | Mg | 12 | Mg2+(aq) or with anions in salts and rocks |
Aluminum (Aluminium) | Al | 13 | Al3+ with anions in rocks and salts, industrially made Al(s) metal |
Silicon | Si | 14 | industrially made Si(s) in computer chips, Si(IV)oxides in sand, glass, most rock |
Phosphorus | P | 15 | phosphates: PO43–, P2O74–, etc in rock, DNA |
Sulfur | S | 16 | S8(s), S2– or sulfate (SO42–) in salts or rocks |
Chlorine | Cl | 17 | Cl–(aq) or with cations in salts, Cl2(g) or ClO–(aq) in disinfectants |
Potassium (kalium) | K | 19 | K+(aq) or with anions in salts, potassium metal (K(s)) only in chem class |
Calcium | Ca | 20 | Ca2+(aq) or with anions in salts and rocks |
Iron | Fe | 26 | Fe(s) metal industrially made, Fe(II) or Fe(III) oxides or sulfides and other minerals |
Copper | Cu | 29 | natural Cu(s) metal, Cu(I) or Cu(II) salts or minerals, usually blue or green |
Bromine | Br | 35 | Br–(aq) or with cations in salts |
Silver | Ag | 47 | natural Ag(s) metal, usually Ag(I) in salts or sulfide minerals |
Tin | Sn | 50 | industrially made Sn(s) in alloys, Sn(II) or Sn(IV) salts and oxide or sulfide minerals |
Iodine | I | 53 | I–(aq) or with cations in salts |
Gold | Au | 79 | natural Au(s) metal, rarely Au(I) or Au(III) salts |
Mercury | Hg | 80 | natural (but rare) metal Hg(l), Hg(II) sulfides and halides, Hg(I) exists as Hg22+ |
Lead | Pb | 82 | Pb(s) in alloys, Pb(II) sulfide, carbonate and sulfate minerals, sometimes Pb(IV) salts or minerals |
Name | Formula | Where you find it |
---|---|---|
Ammonium | NH4+ | soluble salts, fertilizer |
Cyanide | CN– | toxic, in some plant products and dyes |
Hydroxide | OH– | in bases and some minerals |
Peroxide | O22– | in bleaches and disinfectants |
Acetate | C2H3O2– | in vinegar |
Perchlorate | ClO4– | soluble salts and explosives, a strong acid |
Chlorate | ClO3– | similar to perchlorates but less stable |
Chlorite | ClO2– | disinfectants and bleaches, some explosive salts |
Hypochlorite | ClO– | disinfectants and bleaches, most salts unstable |
Nitrate | NO3– | soluble salts, fertilizer, explosives, a strong acid |
Nitrite | NO2– | preservatives for food |
Carbonate | CO32– | in rock, seashells, cement; a base |
Bicarbonate | HCO3– | a base (baking soda), in soda, in blood |
Sulfate | SO42– | in salts, plaster, detergent, a strong acid |
Bisulfate | HSO4– | food additives |
Sulfite | SO32– | salts, food preservatives |
Phosphate | PO43– | salts, rock, fertilizers, a strong acid, in ATP and DNA |