Binary Ionic Compounds

Binary Ionic Compounds (Type I)

1. The cation (positively charged ion; Na^+, Al³⁺) is always named first and the anion (negatively charged ion; Cl^-, O^2-) second.
2. 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 compounds containing this ion.
3. A monatomic anion is named by taking the root of the element name and adding -ide.  Thus, the Cl^- ion is called chloride, the S^2- ion is called sulfide, and the O^2- ion is called oxide.

Some common monatomic cations and anions are shown below
Cation	Name	Cation	Name		Anion	Name	Anion	Name
H+	Hydrogen	Li+	Lithium		H-	Hydride	F-	Fluoride
Na+	Sodium	K+	Potassium		Cl-	Chloride	Br-	Bromide
Cs+	Cesium	Be2+	Beryllium		I-	Iodide	O2-	Oxide
Mg2+	Magnesium	Ca2+	Calcium		S2-	Sulfide	Se2-	Selenide
Ba2+	Barium	Al3+	Aluminum		N3-	Nitride	P3-	Phosphide
Zn2+	Zinc	Ag+	Silver		As3-	Arsenide	C4-	Carbide

Binary Ionic Compounds (Type II)

1. The cation of a transition metal is always 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 parentheses is the charge of the cation.
3. All transition metal cations, except Zn²⁺, Cd²⁺, and Ag⁺ (which always have the charges shown here), must show 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 multiple charges, is named.
4. For the cations in Groups IIIA-VIA (including, Sn, Pb, Ga, Bi, etc.) also have multiple charges, even though they are not transition 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 using 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 first element shown in the compound is named as the element (e.g., for CO₂, first element is "carbon")
2. The second 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 amount of the first element is only shown, if it is present more than once.  It is assumed to be present only once, hence just the name of the element.  However, if it is present more than once, you must then specify 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 compounds:

·         1 — mono ·         2 — di ·         3 — tri ·         4 — tetra ·         5 — penta

·         6 — hexa ·         7 — hepta ·         8 — octa ·         9 — nona ·         10 — deca

Examples using prefixes: CCl4 — carbon tetrachloride P2O5 — diphosphorus pentoxide N2O — ninitrogen monoxide ICl3 — iodine trichloride

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 donor (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 described above.  For example, the sodium salt of nitric acid is sodium nitrate (NaNO₃).  If you know 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 (SO₄^2-) with a -2 charge.
Acids which do not contain 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 single element (not polyatomic), are named as a regular non-metal anion (i.e., Cl^- is chloride, S^2- is sulfide, and F^- is fluoride).

Acid	Name	Anion	Name		Acid	Name	Anion	Name
H2SO4	sulfuric	SO42-	sulfate		HCl	hydrochloric	Cl-	chloride
HNO3	nitric	NO3-	nitrate		HBr	hydrobromic	Br-	bromide
H3PO4	phosphoric	PO43-	phosphate		HClO3	chloric	ClO3-	chlorate
HC2H3O2	acetic	C2H3O2-	acetate		HClO2	chlorous	ClO2-	chlorite
H2SO3	sulfurous	SO32-	sulfite		HBrO3	bromic	BrO3-	bromate
HNO2	nitrous	NO2-	nitrite		HBrO	hypobromous	BrO-	hypobromite

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