Table of Common Ions

Table of "-ates"

Polyatomic oxyanions of nonmetals have formulas that are pretty consistent down a group (family or column). The only real exception to the consistency is nitrate. One easy way to remember the formulas of these ions is to start with boron and phosphorus and count backwards for the charges on each ion: 3–, 2–, and 1– for borate, carbonate, and nitrate; 3–, 2–, and 1– for phosphate, sulfate, and chlorate. The number of oxygens in the "-ate" ion is three for most of them, except phosphate and sulfate, which have four oxygen atoms. Once you know these six (borate, carbonate, nitrate, phosphate, sulfate, chlorate), then it's a matter of remembering that everything below these ions has the same formula as the one above, with only the element being different. Nitrate is the only one that is different from others in its column.

IIA

IIIB

IVB

VIB

VIIB

VIIIB

IIB

IIIA

IVA

VIA

VIIA

VIIIA

BO₃^3–

CO₃^2–

NO₃^–

SiO₃^2–

PO₄^3–

SO₄^2–

ClO₃^–

GeO₃^2–

AsO₄^3–

SeO₄^2–

BrO₃^–

SbO₄^3–

TeO₄^2–

IO₃^–

AtO₃^–

Once you know the table of "-ates", you automatically know the formulas for many other ions and acids if you know the following naming pattern:

Oxyanion and Acid Nomenclature
Pattern	Oxygens vs. -ate	Anion name	Acid Name	Examples
Same charge and one more O atom than "-ate"	+1	per-[root]-ate	per-[root]-ic acid	perchlorate ClO₄^– perchloric acid HClO₄
Root name and formula. Memorize these "-ates"	0	[root]-ate	[root]-ic acid	chlorate ClO₃^– chloric acid HClO₃
Same charge and one fewer O atom than "-ate"	–1	[root]-ite	[root]-ous acid	chlorite ClO₂^– chlorous acid HClO₂
Same charge and two fewer O atoms than "-ate"	–2	hypo-[root]-ite	hypo-[root]-ous acid	hypochlorite ClO ^– hypochlorous acid HClO

Simple ion (one element only, with no oxygens; these are unrelated to the above pattern)	none	[root]-ide	hydro-[root]-ic acid	chloride Cl ^– hydrochloric acid HCl

So, for examples, arsenite is AsO₃^3– and ammonium hypoarsenite is (NH₄)AsO₂. Get it?