How to Master Poly-atomic Ions

I can still think back to sophomore year of high school and blankly starring at a seemingly never-ending list of polyatomic ions and wondering how I was ever going to remember all their charges, names, and elemental make-ups. However, no need to fear over my 5 years of chemistry classes I have been able to adopt a few different techniques to memorizing these bad boys.

For visual and repetition learners:

*I suggest making flashcards with the name on the front, and the elemental composition and charge on the back such as NO₃ ^– .  But I think it is helpful to use colored flashcards and assign each major functional group a color. So all green flashcards are nitrogen groups, all sulfurs are blue ect. There have been many psychology studies done to show that visual learners are able to connect colors with certain topics to have a higher retention rate of a memorized list than just using white cards. It is important to do these card daily- in the car, in-between tv commercials and even to put yourself to sleep at night! The more you involve yourself with these ions the more they become your friends rather than enemies. Also, have other people quiz you and divide the piles between the ones you can and can’t remember to direct your focus on the one’s you still struggle with.

For pattern or systematic learners:

* At first these polyatomic ions may see random and confusing to piece together. However, I can assure you that scientists have put much thought into organizing these and the major patterns are presented below (courtesy of ehow.com as they can write these more eloquently than I) –

*It is easiest to group these polyatomic groups by the main categorizations listed below-

Suffixes

• The suffixes of the names of polyatomic ions have a pattern associated with them. If you will notice, oxyanions end with the prefixs “ate” and “ite.” The key to memorizing the names of oxyanions is knowing the difference between the “ate” and “ite” suffixes. Oxyanions that end with “ate” have one additional oxygen atom; in a symmetric fashion, you can say that oxyanions that end with “ite” have one less oxygen atom. For example, the sulfite ion has three oxygen atoms whereas the sulfate ion has four oxygen atoms.

Prefixes

• In a similar fashion to the suffix pattern, the prefix pattern involved in naming polyatomic ions shows extreme values of oxygen atoms in the ions. The two important prefixes are “per” and “hypo.” If an ion has a “per” prefix, it means the ion has one more oxygen atom than does the ion with as “ate” suffix. On the other side of the spectrum, if an ion has a “hypo” prefix, it implies the ion has one less oxygen atom than does an ion with an “ite” suffix. For example, the perchlorate ion has four oxygen atoms, one more than the chlorate ion; the hypochlorite ion has a single oxygen atom, one less than the chlorite ion.

Hydrogen

• Hydrogen atoms in polyatomic ions bring a positive charge into the ion. This means if you are comparing two ions and you see one has an additional hydrogen atom, you can know its negative charge has been reduced by one. This holds for the addition of multiple hydrogen atoms; for example, two hydrogen atoms reduce the negative charge of the ion by two. For instance, compare hydrogen phosphate (HPO4) with dihydrogen phosphate (H2PO4). If you know the charge of one ion, you need not remember the other. That is, if you know hydrogen phosphate has an ionic charge of -2, you can know dihydrogen phosphate has a charge of -1, since it introduces an extra hydrogen atom.

Acids

• Sulfur and phosphorus play the center roles in polyatomic ions that are acids. Remember the following two rules:
 Acid names with “or” in them imply the inclusion of phosphorus and oxygen, such as phosphoric acid (H3PO4).
Acid names with “ur” in them imply the inclusion of sulfur, as in hydrosulfuric acid (H2S).

For mnemonic learners:

I know throughout my school career I made up songs or sayings to help memorize a wide variety of lists. For example, to remember the biology classifications for animals it is: King Phillip Came over for Good Soup (Kingdom, Phylum, Class, Order, Genus, Species)- I remembered this from over 6 years ago due to its catchy ring! These techniques are super great for memorizing things very long-term. I found this great video (that after watching it a few times can really help memorizing these polyatomic ions).

For those who love rap music I have found this super awesome rapper who can help you rhythm your way to an A (he covers both the charges and the names!)

The Polyatomic rap

I really hope these creative studying techniques and help foster your love of chemistry as it my absolute favorite subject at Rice.

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