When naming compounds, remember the following rules:
Binary Ionic Compounds (Type I)
The cation (positively charged ion; Na+, Al3+) is constantly named first and the anion (negatively charged ion; Cl-, O2-) second.
A monatomic (meaning one-atom) cation takes its name from the name of the element. For example, Na+ is called sodium in the names of compound containing this ion.
A monatomic anion is named by taking the origin of the element name and adding -ide. Thus, the Cl- ion is called chloride, the S2- ion is called sulfide, and the O2- ion is called oxide.
Binary Ionic Compounds (Type II)
- 1. The cation of a transition metal is all the time named first (like any cation) and the anion second.2. A monatomic (meaning one-atom) cation takes its name from the name of the element. For example, Cu+ is called Copper(I) and Cu2+ is called Copper(II) in the names of compounds containing these ions. The number in parenthesis is the charge of the cation.3. All transition metal cations, except Zn2+, Cd2+, and Ag+ (which always have the charges shown here), must illustrate the oxidation number (charge) in parantheses following the English spelling of the element, such as Iron(III), Copper(I), or Vanadium(V), whenever a compound containing these ions, which have numerous charges, is named.4. For the cations in Groups IIIA-VIA (including, Sn, Pb, Ga, Bi, etc.) also have many charges, even though they are not shift metals. For all the metals in these groups (except Al, which, of course, always has a +3 charge), include a paranthesis after the name, and show its positive charge as a Roman numeral (Pb2+ is Lead(II) in names)Binary Covalent Compounds (Type III)Compounds containing only non-metal elements are named with Type III binary compound rules. These compounds are always neutral (not ions which have charges), and consist of only two elements (see acid naming below for compounds containing only non-metal elements, but with more than two elements. The prototypical compound is CO2, which is called carbon dioxide.1. The initial element shown in the compound is named as the element (e.g., for CO2, first element is "carbon")2. The next element shown in the compound is named according to the anion name, ending in -ide (e.g., for CO2, the second element is named "oxide")3. The second element always carries a prefix indicating the number of times it is present in the compound (e.g., for CO2, the second element (oxide) is present twice, so it has the "di" prefix)4. The quantity of the first element is only shown, if it is current more than once. It is assumed to be present only one time, hence just the name of the element. However, if it is present more than once, you must then detail the number of times it is duplicated (di, tri, tetra, etc.)The following prefixes are used to specify the number of times an element is present in binary covalent compounds:
|prefixes (1-5)||prefixes (6-10)||Examples using prefixes|
Please note that ionic compounds (Type I & II binary compound names) never use prefixes to specify how many times an element is present. Prefixes are only used for covalent compounds formed from non-metal elements.
Common Acid and Anion Names
Acids are compounds containing an ionizable proton (H+), since an acid is a proton contributor (a hydrogen atom which has lost its electron). The polyatomic anions derived from acids are named by dropping the -ic (or -ous) suffix from the acid name and adding the -ate (or -ite) suffix, respectively. Compounds containing polyatomic anions are named using the Type I or Type II naming systems illustrated above. For example, the sodium salt of nitric acid is sodium nitrate (NaNO3). If you recognize the acid formula you will always get the correct anion formula and its charge, since the charge is equal to the number of ionizable hydrogen atoms in the acid, and is always negative. For example, for sulfuric acid (H2SO4), the anion is sulfate (SO42-) with a -2 charge.
Acids which do not have oxygen (e.g., HCl, H2S, HF) are named by adding the hydro- prefix to the root name of the element, followed by the -ic suffix. HCl is hydrochloric acid, H2S is hydrosulfuric acid, and HF is hydrofluoric acid (italics added for emphasis). Anions of these acids, which contain a lone element (not polyatomic), are named as a regular non-metal anion (i.e., Cl- is chloride, S2- is sulfide, and F- is fluoride).