Note: this list contains commonly-found oxidation states. Often, a polyatomic ion can be considered as the conjugate acid or base of a neutral molecule. For example, do you know the formula for chromate? acetate CH 3COO-1 acetylide -C 2 2 americyl AmO 2 +2 amide -NH 2 1 +1 ammonium +1NH 4 arsenate AsO 4-3 arsenite AsO 3-3-astatate AtO 3-1 azide -N 3 1 benzoate -C 6H 5COO-1 bicarbonate/hydrogen carbonate 3 HCO -1 binoxalate/hydrogen oxalate HOOCCOO-1 bismuthate BiO 3-1 bisulfate/hydrogen List of Common Ions Polyatomic Cations NH4 + ammonium H3O + hydronium Polyatomic Anions OH-hydroxide CN-cyanide O2 2-peroxide CO3 2-carbonate C2O4 2-oxalate NO2-nitrite NO3-nitrate PO3 3-phosphite PO4 3-phosphate SO3 2-sulfite SO4 2-sulfate S2O3 2-thiosulfate ClO-hypochlorite ClO2-chlorite ClO3-chlorate ClO4-perchlorate CH3COO or C2H3O2-acetate AsO4 3-arsenate For example, the conjugate base of sulfuric acid (H 2 SO 4) is the polyatomic hydrogen sulfate anion (HSO − … Common Ions You Need to Know. * Also, a common mistake I see is people thinking helium is a diatomic molecule (He 2). The DAT general chemistry section expects you to be fluent in chemical compounds. Polyatomic ions are formed every time a molecule must gain or lose electrons, so that all the atoms of the molecule can obtain the rule of the octet. In order to name them, you will need to memorize some of the typical polyatomic ions, but in case you have not done so, you could also look for a list of polyatomic ions. The tables below list common polyatomic ions that you will be using throughout this General-Chemistry laboratory series (Chem 151-152). Chemistry I Polyatomic Ions Here’s a list of common polyatomic ions and acids: Ion Name Acid Formula Acid Name NH4 + Ammonium* NO3-Nitrate HNO3 Nitric Acid NO2-Nitrite HNO2 Nitrous Acid OH-Hydroxide* HOH Water (not really an acid) CN-Cyanide HCN Hydrocyanic Acid SCN-Thiocyanate HSCN Thiocyanic Acid ClO4-Perchlorate* HClO4 Perchloric Acid Learn vocabulary, terms, and more with flashcards, games, and other study tools. Polyatomic ions often are useful in the context of acid-base chemistry, and in the formation of salts. Title: Microsoft Word - Polyatomic Ion Reference Sheet.doc Author: Tad&Rose Created Date: 6/10/2007 4:04:00 PM Start studying Polyatomic Ions List. POLYATOMIC IONS Polyatomic ions are made up of two or more atoms that are stuck together and will often travel as a group during a chemical reaction. Below is a selected list of common ions you should know for the DAT (click for full image). For example, the conjugate base of sulfuric acid (H 2 SO 4) is the polyatomic hydrogen sulfate anion (HSO − … These ions are separated by charge on the ion into four (4) different tables and listed alphabetically within each table. Often, a polyatomic ion can be considered as the conjugate acid or base of a neutral molecule. Other oxidation states are commonly encountered for metals in polyatomic ions, where the metal is not the cation of a compound. Oxidation states not shown exist, but they are less-frequently encountered and therefore not "common." Polyatomic Ions . Polyatomic ions often are useful in the context of acid-base chemistry and in the formation of salts.