How to Name & Write Acids and Bases

How to Name & Write Acids and Bases

Many find it difficult to name acids and bases, not knowing whether they should use the prefix “hydro-“, or maybe the suffix “-ous”. In some cases you might need neither prefixes nor suffixes. Sometimes you might not know the names of the ions, in other instances you might not know which prefix to use. All this takes is a bit of time to memorize, but don’t worry because there aren’t many rules on how to name acids and bases.

Before I get into naming acids and bases, I’ll set off the basics you should know. What are anions and polyatomic ions? First of all, ions are just charged atoms or molecules. An anion is a negatively charged ion. Don’t get it confused with the cation, a positively charged ion. A polyatomic ion is an ion composed of two or more covalently bonded atoms. There are different kinds of acids. Two common kinds of acids are binary and oxyacids. A binary acid is a hydrogen bond with a non-metal. For examples HCl, it has one hydrogen bonded to a chlorine. An oxyacid is a molecule with one or more OH bonds. For example HNO3, with one hydrogen, one nitrogen and three oxygens, and also HClO2, which has one hydrogen, one chlorine, and two oxygens.

In order to name binary acids, all you simply have to do is find the root of the anion, add the prefix “hydro-” and the suffix “-ic” to it, and place the word acid right after it. For example H2S would be called hydrosulfuric acid. We used the prefix hydro-, the root of the anion sulfur, the suffix -ic, and the word acid. Naming oxyacids can get a little more complicated. There are different kinds of oxyacids. To be able to name these, you would have to memorize the some of the common polyatomic ions, but if you haven’t, you could also look for a list of polyatomic ions. If the polyatomic ion ends with the suffix “-ate” just switch it out with “-ic” and add the word acid after it. In this case, the polyatomic ion of ClO3 is chlorate, the acid would be called chloric acid. IF it has one extra oxygen, instead of switching to -ous, you’ll switch it to -ic AND add the prefix “per-” to it. So ClO4 is called perchloric acid. IF the compound has one less oxygen than the acid with the ion ending with -ate, it will end with the suffix “-ous” and the word acid. So ClO2 would be called chlorous acid. IF it has two less oxygens, you add the prefix “hypo-“, the suffix “-ous”, and the word acid to the root of the anion. ClO would be called hypochlorous acid.

Bases are ionic compounds. Naming bases has a lot less to it, but will also take some memorization unless you have a list with common polyatomic ions. A lot of the strong bases contain OH, hydroxide. To name bases, you use the name of the ion bonded to the OH and add the word hydroxide after it. NaOH would be sodium hydroxide. There are some ions that don’t follow any naming structure, for example NH4 is called ammonium. So NH4OH is called ammonium hydroxide. Then there are the weaker bases that don’t contain OH in them. These are cases in which you will need a polyatomic ions list because the names do not follow any naming system. For example Ca(NH2)2 is called calcium amide.

Naming acids and bases requires you to remember when to use certain prefixes and suffixes, all that takes a bit of practice to ultimately master. Once you begin to memorize them you’ll be able to name like it were an everyday thing. Naming them isn’t really as hard as it seems. I’d encourage you all to attempt to memorize at least some of the common polyatomic ions, because you won’t always have access to a list giving you all their names. Take your time and just think of it as learning new vocabulary words.

So, what is it that makes some acids and bases stronger than others? There are several factors as to what affects their acidity. First factor: the number of hydrogens. Say we have HCl, H2Cl is more acidic than HCl, but less acidic than H3Cl. So HCl < H2Cl < H3Cl. A second factor has to do with electronegativity and size. The farther right and element is in the periodic table, meaning the more electronegative it is, the stronger the acid is. This works the opposite way when moving vertically through the periodic table. The lower it is on the periodic table, the lower its electronegativity, the stronger the acidity becomes. There are other factors that change the acidity, but those are more complicated, like orbitals for example. What about bases? Well bases are defined as stronger when they are bonded to a hydroxide (OH). When these bases dissolve they give out the hydroxide. Unlike strong bases, weaker ones don’t have a hydroxide, and rather than giving it out, they gain a hydroxide when they react with water. Most weak bases derive from anions in weak acids. Acids and bases are named both in different ways, but each can be learned with only a bit of practice.

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