IndietroEssential Polyatomic Ions for General Chemistry
Guida di studio - Note intelligenti
Appunti personalizzati basati sui tuoi materiali, ampliati con definizioni chiave, esempi e contesto.
Polyatomic Ions
Introduction to Polyatomic Ions
Polyatomic ions are charged species composed of two or more atoms covalently bonded, acting as a single unit with a net positive or negative charge. Memorizing common polyatomic ions is essential for understanding chemical nomenclature, writing chemical formulas, and predicting the products of chemical reactions.
Polyatomic anions carry a negative charge and are commonly found in ionic compounds.
Polyatomic cations are less common, with ammonium being the most notable example.
Many polyatomic ions contain oxygen and are called oxyanions.
Common Polyatomic Anions
The following table lists essential polyatomic anions, their formulas, and charges. These ions are frequently encountered in general chemistry courses and laboratory settings.
Name | Formula | Charge |
|---|---|---|
Nitrate | NO3- | -1 |
Nitrite | NO2- | -1 |
Hydroxide | OH- | -1 |
Permanganate | MnO4- | -1 |
Acetate | C2H3O2- or CH3COO- | -1 |
Hydrogen Carbonate (Bicarbonate) | HCO3- | -1 |
Hydrogen Sulfate | HSO4- | -1 |
Hydrogen Sulfite | HSO3- | -1 |
Dihydrogen Phosphate | H2PO4- | -1 |
Perchlorate | ClO4- | -1 |
Chlorate | ClO3- | -1 |
Chlorite | ClO2- | -1 |
Hypochlorite | ClO- | -1 |
Iodate | IO3- | -1 |
Hypoiodite | IO- | -1 |
Bromate | BrO3- | -1 |
Hypobromite | BrO- | -1 |
Cyanide | CN- | -1 |
Cyanate | OCN- | -1 |
Thiocyanate | SCN- | -1 |
Azide | N3- | -1 |
Peroxide | O22- | -2 |
Sulfate | SO42- | -2 |
Sulfite | SO32- | -2 |
Thiosulfate | S2O32- | -2 |
Carbonate | CO32- | -2 |
Chromate | CrO42- | -2 |
Dichromate | Cr2O72- | -2 |
Oxalate | C2O42- | -2 |
Monohydrogen Phosphate | HPO42- | -2 |
Phosphate | PO43- | -3 |
Phosphite | PO33- | -3 |
Arsenate | AsO43- | -3 |
Arsenite | AsO33- | -3 |
Common Polyatomic Cations
Ammonium is the most common polyatomic cation encountered in general chemistry.
Name | Formula | Charge |
|---|---|---|
Ammonium | NH4+ | +1 |
Naming and Recognizing Polyatomic Ions
Names ending in -ate and -ite indicate oxyanions, with -ate having more oxygen atoms than -ite (e.g., sulfate SO42- vs. sulfite SO32-).
Prefixes such as per- (more oxygen) and hypo- (less oxygen) further distinguish related ions (e.g., perchlorate ClO4-, chlorate ClO3-, chlorite ClO2-, hypochlorite ClO-).
Hydrogen or dihydrogen in the name indicates the presence of one or more hydrogen atoms (e.g., hydrogen carbonate HCO3-).
Examples and Applications
Sodium sulfate contains the sulfate ion: Na2SO4.
Ammonium nitrate contains both ammonium and nitrate ions: NH4NO3.
Calcium carbonate is found in limestone and chalk: CaCO3.
Key Formulas
When writing formulas for ionic compounds containing polyatomic ions, use parentheses if more than one polyatomic ion is present. For example:
Here, two nitrate ions are needed to balance the +2 charge of calcium.
Summary Table: Polyatomic Ions by Charge
Charge | Examples |
|---|---|
-1 | Nitrate, Nitrite, Hydroxide, Permanganate, Acetate, Bicarbonate, etc. |
-2 | Sulfate, Sulfite, Carbonate, Chromate, Dichromate, Oxalate, Thiosulfate, Peroxide, Monohydrogen Phosphate |
-3 | Phosphate, Phosphite, Arsenate, Arsenite |
+1 | Ammonium |
Additional info:
Memorizing these ions is crucial for success in chemical nomenclature, balancing equations, and understanding solubility rules.
Some ions have multiple accepted names (e.g., hydrogen carbonate is also called bicarbonate).
