Phosphate is PO43- Phosphite is PO33- QUESTION: Which of the following polyatomic ions is not paired with its correct formula? A. chlorite, ClO2-, B. hypochlorite, ClO- C. phosphite, PO2-, D. sulfite, SO32- Phosphate is PO43- Phosphite is PO33- Chlorate is ClO3- Chlorite is ClO2- Sulfate is SO42- Sulfite is SO32- Phosphite is PO33-. Names and formulas of polyatomic ions are trivial information --- just memorize. Tip: memorize ions with names ending in “ate”; With “ite” ending: one less O, same charge SCRIPT: Which of the following polyatomic ions is not paired with its correct formula? Chlorite… hypochlorite… phosphite… or sulfite PAUSE CLICK The correct answer is C. The correct formula of phosphite is PO3 with a –3 charge. 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. Whether or not your teacher requires you to memorize them, it’s a good idea to just memorize them. CLICK It’s a good idea to memorize formulas of ions with names ending in “ate” HIGHLIGHT “ate” because… The formulas of ions with names ending in “ite” will simply have one less oxygen, and the same charge. For example, If you know that sulfate is SO4 with a –2 charge. Then you should be able to figure out that sulfite has one less oxygen, with the same charge. So, sulfite is SO3 with a –2 charge. CLICK Similarly, phosphate is PO4 with a –3 charge. Phosphite, has one less oxygen and the same charge. Phosphite is PO3 with a –3 charge. If you know that chlorate is ClO3 with a –1 charge. Then you should be able to figure out that chlorite has one less oxygen, with the same charge. So, chlorite is ClO2 with a negative one charge. Here’s another tip… If you see a hypo prefix HIGHLIGHT hypo That means one less oxygen, same charge. A hypo prefix is only written in front of a name that ends in ite. As in choice B. Remember that chlorite is ClO2 with a –1 charge. Therefore, hypochlorite is ClO with a –1 charge. CLICK PAUSE END RECORDING A “hypo” prefix means one less oxygen, same charge.

Video ID: 1-22-4 © 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