Roman Numerals and Latin Names

When a metal ion has more than one possible charge then the charge must be indicated in some way.

Roman Numerals

The standard way to do exprss charge is to use a roman numeral. Thus Cu+2 would be labeled copper II and Cu+1 would be labeled copper I.

In case you've forgotten (or never knew) the roman numerals from 1 to 10 are:

1 I 6 VI
2 II 7 VII
4 IV 9 IX
5 V 10 X


Latin Names

If a metal ion has only two possible charges, there is an older way to label the charge which is still in use. This involves taking the latin root of the element's name and adding the ending "ic" for the higher charge or "ous" for the lower charge. (That's easy to remember because ic and high both have the letter i in them and ous and low both contain the letter o.

Here are some of the commonly used elements, their latin roots and the roots with the two possible endings.

element root higher charge lower charge
Copper cuprum cupric cuprous
cobalt cobalt cobaltic cobaltous
gold aurum auric aurous
nickel nickel nickelic nickelous
tin stannum stannic stannous
lead plumbum plumbic plumbous
iron ferrum ferric ferrous

Of course to use this you will need to be able to determine the charge on the ion.

So the compound NiSO4 would be called either nickel II sulfate or nickelous sulfate, while the compound Ni2(SO4)3 would be called either Nickel III sulfate or nickelic sulfate.


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