Some strategies for memorization: QUESTION: Which of the following polyatomic ions is not paired with its correct formula? A. sulfate, SO42-, B. carbonate, CO42- C. phosphate, PO43-, D. perchlorate, ClO4- Carbonate is CO32- Names and formulas of polyatomic ions are trivial information --- just memorize. Some strategies for memorization: Read the names formulas aloud several times. Make up memory aids; find patterns. Work on drills (reading/writing formulas of compounds). Use it or lose it! SCRIPT: Which of the following polyatomic ions is not paired with its correct formula? Sulfate,… carbonate… phosphate… or perchlorate PAUSE CLICK All of the formulas given are correct, except for carbonate. The correct answer is choice B. CLICK The formula for carbonate is CO3 with a –2 charge, not CO4 with a –2 charge. CLICK Names and formulas of polyatomic ions are trivial information. In other words, you just need to memorize them as part of the basic vocabulary of Chemistry. Be sure to memorize not just the elements and subscripts, but also the charge. The charge is part of the formula. Whether or not your teacher requires you to memorize them, it’s a good idea to memorize them. Here are some strategies that you can use for memorization. CLICK Refer to a list of names and formulas. Read the names formulas aloud several times. Hearing and seeing should help you remember better than just seeing. Make up memory aids. Try to find patterns in the names and formulas. Work on drills, such as reading or writing of formulas of compounds, that require you to remember these information. Remember that if you don’t use this information, you’re likely to forget it. CONTINUED ON NEXT SLIDE

Memory aid: Oxoanions with 4 oxygen atoms, “ate” PO43-: Phosphate AsO43-: Arsenate SeO42-: selenate SO42-: sulfate P As Se S 4 3 2 Here’s an example of a memory aid to remember oxoanions with 4 oxygen atoms, with names ending in “ate” Four of these ions are phosphate, arsenate, selenate, and sulfate. Note that they all have four oxygen atoms. If you look at the symbol of the other element, they spell the word “passes” The charges, on the other hand, are –3 for phosphate and arsenate,… HIGHLIGHT charges in the formulas and –2 for selenate and sulfate. HIGHLIGHT chargesinthe formulas SO, a good way to remember these four ions is to use the phrase “Passes four three two” HIGLIGHT “P As Se S 4 3 2” Phosphate, arsenate, selenate, and sulfate HIGHLIGHT “P As Se S” in “P As Se S 4 3 2” all have four oxygens HIGHLIGHT “4” in “P As Se S 4 3 2” and their charges are –3 and –2. HIGHLIGHT “3 2” in “P As Se S 4 3 2” Let’s see if we can relate this information to the periodic table. CLICK You can see from the periodic table that phosphorus and arsenic are in group five A. CLICK CLICK While selenium and sulfur are in the next column… group six A. You can also relate this information to the formulas and names of the corresponding monatomic ions. Phosphide and arsenide both have a charge of –3. HIGHLIGHT Whereas sulfide and selenide both have a charge of –2. PAUSE CLICK END RECORDING Monatomic ions: P3-: Phosphide, S2-: sulfide As3-: arsenide, Se2-: selenide

Video ID: 1-22-1 © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08