University:
Glendale Community College
Course:
CHM151 | General Chemistry
Academic year:

2021
Views:

101

Pages:

2
Author:

Kyson Owen

Key Polyatomic Ions to Know for General Chemistry First, and most importantly, MEMORIZE these 16 polyatomic ions… 2+ Cation Hg2 2+ mercury(I)* 1+ Cations 0 1– Anions NH4 + ammonium CN– H3O + hydronium 2– Anions SO4 2– sulfate NO3 – nitrate CO3 2– carbonate OH – hydroxide CrO4 2– chromate N3 – azide Cr2O7 2- dichromate cyanide CH3COO – O2 2– or C2H3O2 – acetate MnO4 – permanganate ClO3 – chlorate *In the diatomic mercury(I) ion, each mercury atom has lost one electron (for a charge of 2+ for the diatomic pair) (Please see the next page for other polyatomic ions you need to know) peroxide 3– Anions PO4 3– phosphate …and THEN use these three patterns to help you learn many more ions than you have memorized: Pattern 1. Naming based on “ate”. Whenever a polyatomic anion ending in “-ate” has oxygens in it (“oxyanions”), there may be derivatives of that anion with a different number of oxygens. When this happens, the charge does not change. The regular pattern for naming these is as follows: Change in # oxygens Prefix & Suffix becomes Example: Example: Example: chlorine based oxyanions nitrogen based oxyanions sulfur based oxyanions -ate ClO4 – perchlorate Starting at “-ate” -ate ClO3 – chlorate NO3 – nitrate SO4 2- sulfate -1 oxygen -ite ClO2 – chlorite NO2 – nitrite SO3 2- sulfite -ite ClO – or OCl – hypochlorite +1 oxygen per- -2 oxygens hypo- Pattern 2. Group relationships. Often, elements within a group have the same number of oxygens in their “-ate” oxyanion (though charges are different). A notable exception to this pattern is nitrate, which has only three oxygens, even though others in its group have four: Period 2 3 Group 14 “-ate” oxyanions CO3 2SiO3 2- Group 15 “-ate” oxyanions NO3 – carbonate silicate PO4 3AsO4 3- 4 Group 16 “-ate” oxyanions Group 17 “-ate” oxyanions nitrate sulfate ClO3 – chlorate SeO4 2- selenate BrO3 – bromate TeO4 2- tellurate IO3 – iodate phosphate SO4 2- arsenate 5 Pattern 3. Hydrogen-containing polyatomic anions. When hydrogen is added to a polyatomic anion to make a new anion, it increases the charge by +1: CO3 2– carbonate HCO3 – hydrogen carbonate (or bicarbonate**) SO4 2– sulfate HSO4 – hydrogen sulfate (or bisulfate**) PO4 3– phosphate HPO4 2– hydrogen phosphate H2PO4 – dihydrogen phosphate ** The International Union of Pure and Applied Chemistry has recommended that use of the names bicarbonate and bisulfate be discontinued. Remember: For simple MONOatomic anions…when a single atom becomes an anion by gaining one or more electrons, it takes an “-ide” ending to show that it is now a monoatomic anion, for example: N is nitrogen but N3- is nitride, O is oxygen but O2- is oxide, F is fluorine but F- is fluoride, H is hydrogen but H– is hydride.