Naming Simple Compounds. I. Binary compounds : are those composed of only two elements. 1 ) Binary compounds of metals and nonmetals.
When use old group number- Roman numeral plus letter A or B, the charge on a cation for main-group element, in most cases, equals the group number ( the Roman numeral).
For example, aluminum, which is in group IIIA, has an ion with charge 3+. Some exceptions are noted for elements of high atomic number such as lead, in group IVA, whose common ion is Pb 2+. The charge on an anion euals the group number minus 8. Oxygen, in group VIA, has an anion charge of 2-(6-8).
Most transition elements have cations of several different charges (see Table 4.2). For example, iron has the cations Fe2+ and Fe3+.
Table 4.2 Some Common Ions of the Transition Elements: only ions
- The overall zero charge is provided for by adjusting the ratio of cations and anions.
tin(II) fluoride SnF2calcium chlorideCaCl2
silver sulfide Ag2S chromium(III) chloride CrCl3
The main group metals and nonmetals form ions related to their group number.
carbon monoxide carbon dioxide
boron trichloride carbon tetrachloride
dinitrogen monoxide diboron tetrabromide
phosphorus pentachloride sulfur hexaflouride
An element common to many polyatomic ions is oxygen, usually in combination with another nonmetal. Such anions are called oxoanions. Certain nonmetals such as Cl, N, P and S from a series of oxoanions containing different numbers of oxygen atoms. When an element has two oxoanions, the name of the one with higher oxidation state (more oxygens) ends in –ate; the name of the one with lower oxidation state (less oxygen) ends in –ite.