Inorganic compounds can be ionic or covalent. The rules for naming these differ slightly. We'll examine ionic compounds first.
Naming Ionic Compounds
Before you can name ionic compounds you must first recognize that you have an ionic compound. Ionic compounds contain metal and nonmetal elements. You should also be able to determine which metal ions can form only one ion. Elements in groups IA, IIA, & IIIA (except Tl) form only one ion which will be the same number as the group number. To determine the ion charge for a monoatomic nonmetal ion subtract the group number from eight. For example, the oxide ion carries a -2 charge. Oxygen is a group VIA element. Subtract 6 from 8, 6 - 8, and you'll end up with a -2 charge. You'll need to memorize the polyatomic ions. You'll also need to be familiar with the formulas and charges of some of the more commonly used ions. Refer to the following tables for these.
TABLE OF CATIONS
| +1 charge | +2 charge | +3 charge | +4 charge |
| H+ hydrogen |
Ca2+ calcium |
Al3+ aluminum |
Si4+ silicon |
| Li+ lithium |
Be2+ beryllium |
Fe3+ iron(III) |
Sn4+ tin(IV) |
| K+ potassium |
Ba2+ barium |
Pb4+ lead(IV) |
|
| Na+ sodium |
Cu2+ copper(II) |
||
| Ag+ silver |
Fe2+ iron(II) |
||
| Cu+ copper(I) |
Mg2+ magnesium |
||
| NH4+ ammonium |
Zn2+ zinc |
||
| Sn2+ tin(II) |
|||
| Hg2+ mercury(II) |
|||
| Ni2+ nickel |
|||
| Pb2+ lead(II) |
|||
TABLE OF ANIONS
| -1 charge | -2 charge | -3 charge | -4 charge |
| F- fluoride |
O2- oxide |
PO43- phosphate |
C4- carbide |
| Cl- chloride |
S2- sulfide |
P3- phosphide |
|
| Br- bromide |
CO32- carbonate |
N3- nitride |
|
| I- iodide |
SO42- sulfate |
||
| OH- hydroxide |
HPO42- hydrogen phosphate |
||
| CN- cyanide |
|||
| HCO3- hydrogen carbonate (bicarbonate) |
|||
| NO2- nitrite |
|||
| NO3- nitrate |
|||
| CH3CO2- acetate |
|||
| H2PO4- dihydrogen phosphate |
|||
| HSO4- hydrogen sulfate |
|||
RULES FOR NAMING IONIC COMPOUNDS
1. The cation (metal ion) will use the element name. If it can form just one ion, you do not need to use a stock number (Roman numeral). If it can form more than one ion, use a stock number equal to the charge of the ion. Example, Na+ can only form one ion so you will not use a stock number. Cu2+ will use a stock number of 2, copper(II), (read as copper 2), since it can form both a +1 ion and +2 ion.
2. If you have a monoatomic anion, add the prefix -ide to the first (sometimes two) syllable of the element name. Examples, O2- will be oxide, Cl- will be chloride, I- will be iodide, Se2- will be selenide. If you have a polyatomic ion, simply use its name. Examples, SO42- will be sulfate, NO3- will be nitrate and so on.
3. In naming compounds, the cation goes first, then the anion.
4. The overall charge of an ionic compound should be zero. When you combine atoms or groups to form a compound, the key is to make sure that the overall charges are balanced.
Try the following examples. The answers are located at the end of this worksheet:
1. CaSO4
2. Ni(NO3)2
3. Fe2(CO3)3
4. Ti(ClO4)4
5. PbC2O4
6. NaBr
7. K2S
8. Mg3N2
9. Cr2O3
10. AlCl3
Naming Binary Covalent Compounds
The naming of covalent compounds is much easier than naming ionic compounds. Here, you use prefixes to denote how many of a specific element is present. The common prefixes are:
| 1 - mono | 7 - hepta |
| 2 - di | 8 - octa |
| 3 - tri | 9 - nona |
| 4 - tetra | 10 - deca |
| 5 - penta | 11 - hendeca |
| 6 - hexa | 12 - dodeca |
1. Name the first element using the element's name. If there is more than, use the appropriate prefix. Never use the mono prefix for the first element and always use a prefix for the second element (also, it's monoxide, not monooxide).
2. Use the appropriate prefix for the second element and add the -ide suffix to the end. If the second element name starts with a vowel, and your prefix ends with an a, drop the a from the prefix.
Try the following examples. The answers are located at the end of this worksheet:
1. CO2
2. P4O10
3. NCl3
4. SiS2
5. SeBr2
6. CO
7. S2F6
8. N2O4
9. PBr5
10. N2F4
Naming Acids
1. Some types of acids are formed by adding H+, (hydrogen ion), to a monatomic anion. For this type of acid, begin the name with "hydro", drop the "-ide" suffix for the anion and add the suffix "-ic". For example, HBr will be hydrobromic acid.
2. Oxyacids have polyatomic anions such as nitrite and carbonate. To name an acid ending in "-ite", drop the "-ite" and add "-ous". Example, HNO2, will be nitrous acid. For acids that end in "-ate", drop the "-ate" and add "-ic". Example, H2CO3, will be carbonic acid.
3. Oxyacids of Group VII elements, (halogens), are a little more tricky because there are four different possibilities for oxyanions. You would still use the "-ite"/"ous" and "-ate"/"ic" rules. Prefixes of "hypo-" or "per-" are used for the anion as well as the acid name.
This example uses the halogen chlorine:
ClO- (hypochlorite ion). Acid name - hypochlorous acid (HClO)
ClO2- (chorite ion). Acid name - chlorous acid (HClO2)
ClO3- (chlorate ion). Acid name - chloric acid (HClO3)
ClO4- (perchlorate ion). Acid name - perchloric acid (HClO4)
Answers for ionic compounds:
1. calcium sulfate
2. nickel(II) nitrate
3. iron(III) carbonate
4. titanium(IV) perchlorate
5. lead(II) oxalate
6. sodium bromide
7. potassium sulfide
8. magnesium nitride
9. chromium(III) oxide
10. aluminum chloride
Answers for binary compounds:
1. carbon dioxide
2. tetraphosphorus decoxide
3. nitrogen trichloride
4. silicon disulfide
5. selenium dibromide
6. carbon monoxide
7. disulfur hexafluoride
8. dinitrogen tetroxide
9. phosphorus pentabromide
10. dinitrogen tetrafluoride