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Contents
- Introduction What are polyatomic ions? Why learn about them? What's in this guide?
- Beginner's guide to polyatomic ions Ions any first year student should know.
- Arranged by family
- Common naming guidelines Remembering a few prefixes and suffixes makes learning the lists much simpler.
- Arranged by charge
- Quiz on polyatomic ions
- Resources and references
Introduction
Polyatomic ions are charged molecules
. The atoms within a polyatomic ion are usually very tightly bound together,
so the ion retains its identity within ionic compounds and over the course of many chemical reactions.
Because polyatomic ions are basic building blocks of so many ionic compounds, learning the names, charges, and formulas of the most common polyatomic
ions is absolutely essential before many other skills can be mastered. Those skills include:
- writing down empirical formulas for ionic compounds
- naming ionic compounds
- reading and correctly interpreting labels on reagent bottles
- naming inorganic
acids
- predicting the solubility of an ionic compound
- predicting the products of a reaction between aqueous ionic compounds
- predicting the products of neutralization reactions
- writing and balancing ionic equations
- writing and balancing redox equations
- understanding environmental chemistry (e. g. mechanisms in acid rain formation and water quality assessment)
- understanding geochemistry (e. g. composition and formation of minerals)
- understanding clinical and biological chemistry (e. g. electrolyte balance and buffering in blood)
First year students are often asked to memorize lists of polyatomic ions without any context.
Mnemonics can be helpful, but they provide an artificial way to organizing what must be memorized.
This beginner's guide to polyatomic ions will eventually provide a relevant context for students learning the names and formulas of polyatomic ions by answering these questions:
Where do polyatomic ions come from? Where are they found in nature? Why are they important? What do they do? What do they look like? How are they used?
Beginner's guide to polyatomic ions
The following tables list polyatomic ions that any first year student should know. (Common monoatomic ions can be found elsewhere).Ions arranged by family
Polyatomic cations other than ammonium, hydronium, and mercury(I) aren't usually encountered in general chemistry.Most common polyatomic anions occur in "families". All members of the family share the same central element and the same charge. There are three common types of variations within the family:
- Different members of the family can have numbers of oxygens.
- Each member of the family can combine with hydrogen ions to partially neutralize their negative charge.
- Some members of the family can have sulfur substituted for oxygen.
Table of common polyatomic cations, arranged by family. Alternate names are given in italics. Select the name of the ion for information about its occurrence, uses, properties, and structure. Blank entries are uncommon or unstable; for a complete table see the Field Guide to Polyatomic Ions.
| carbon | nitrogen | sulfur | chlorine | ||||||||||||||||||||||||||||||||||||||||||||||
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| phosphorus | cyanide | cations | metal oxyanions | ||||||||||||||||||||||||
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| oxygen | organics | ||||||
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Common naming practices
| modify stem name with: | meaning | examples |
| -ate | a common form, containing oxygen |
chlorate, ClO3- nitrate, NO3- sulfate, SO42- |
| -ite | one less oxygen than -ate form |
chlorite, ClO2- sulfite, SO32- nitrite, NO2- |
| per-, -ate | same charge, but contains one more oxygen than -ate form |
perchlorate, ClO4- perbromate, BrO4- |
| hypo-, -ite | same charge, but contains one less oxygen than the -ite form | hypochlorite, ClO- hypobromite, BrO- |
| thio- | replace an O with an S |
thiosulfate, S2O32- thiosulfite, S2O22- |
| modify stem name with: | meaning | examples |
| hydrogen or bi- |
(1) captured H+ ions |
hydrogen carbonate, HCO3- (a.k.a. bicarbonate) hydrogen sulfate, HSO4- (a.k.a. bisulfate) |
| dihydrogen | (2) captured H+ ions | dihydrogen phosphate, H2PO4- |
Table of common polyatomic cations, arranged by charge. Alternate names are given in italics. Select the name of the ion for information about its occurrence, uses, properties, and structure.
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Resources
- Nomenclature of Inorganic Chemistry (IUPAC)
- Primary source for formulas and names in the field guide section (International Union of Pure and Applied Chemistry, Nomenclature of Inorganic Chemistry, 2nd Edition, Butterworths, London, 1979)
- Inorganic Chemical Nomenclature (IUPAC)
- Bibliography of IUPAC publications on inorganic nomenclature.
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General Chemistry Online! Polyatomic ions
Copyright © 1997-2005 by Fred Senese
Comments & questions to fsenese@frostburg.edu
Last Revised 12/14/21.URL: http://antoine.frostburg.edu/chem/senese/101/compounds/polyatomic.shtml