Okay, so as we know, naming chemicals is a horible, boring, time consuming task. I mean who looks at a substance like this and knows immediately that it just so happens to be 5-bromo-5-iodohexan-2,3-diol. Or Steve, as my friend ended up calling it. Personally, it strikes me more as a Bruce, but each to their own I suppose.
The first step to being able to name these overly-complicated, but not completely useless compounds, is to be able to recognise the individual elemental symbols and their names.
Now, I’m not a fan of rote-learning at all but sometimes that’s just what it takes to master it.
The easy part for most simple compounds is the cation, or positive ion, if you prefer. These include things like sodium (Na+), magnesium (Mg+) or even iron (III) (Fe3+). The nams of cations tend to stay the same as their normal name.
Anions, or negative ions, are a little bit harder. Their normal names change. As an example, for a simple monatomic, like chlorine, the suffix changes to -ide. Same for fluorine and iodine. When we say chlorine, we mean the element chlorine, symbol Cl. It hasn’t lost or gained any electrons. When it gains an electron, it changes its name (what a lot of paperwork) to chloride.
A word of warning: if you mix them up more than once, I will hunt you down and I will hurt you and make sure you never mix them up again. I am a teacher, do not doubt me.
Just remember, cations first and the anion’s name changes slightly.
When chemists talk about ions, there’s usually some mention of this thing, valency. “What is this?” you ask. Well, short answer: it just means the charge on the ion. Sodium has a valency of 1, chlorine has a valency of -1. Most metals have multiple valencies, just look at iron (I), iron (II) and iron (III). So, when we have ions with different valencies, we have to make sure they balance out so that the overall molecule’s charge is 0. The easiest way to do this is using the “crossover” method.
Ignore the signs, they’re just there to remind you that they are charged.
So, write the charge on top of each ion. Cross them over and then write the number as a subscript. For aluminium oxide to be a molecule, the charges have to equal zero overall. So, since aluminium has a valency of +3, we need 1.5 oxygen ions to cancel that out. The chemical equation for aluminium oxide looks something like Al2O3.
So, those are the basic rules for naming compounds ionic compounds (they are made up of ions). The rules for naming molecular compounds are pretty similar, but we use prefixes like mono-, di-, tri- etc… For these, its whatever happens to be written first.
For example, N2O4 (please imagine that the numbers are subscripts) is called dinitrogen tetraoxide.
Here are some websites that have some good stuff to help you practise:
– Wolfram
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