Roman Numeral

[Adrienne_4F]

Some of the names of molecules have roman numerals. How do we know which ones have roman numerals and what the roman numerals are?

[Rachana Jayaraman 1H]

The Roman numerals represent the oxidation number of the central metal atom/ion. The oxidation number of the metal atom and the oxidation numbers of the other ligands should add up to the overall charge on the coordination compound/ion.

[amogha_koka3I]

An example is [Fe(CN)₆]4−. The oxidation state of the compound is 4- and the number for CN is -1 for 6 molecules so it is -6. You then subtract -6 from -4 to get the +2 oxidation number for Fe.

[yuetao4k]

The roman numerals correlate with the transition metal's oxidation number. Ag, Fe, Cu, and Pb are some examples of elements that need a roman numeral when naming them.

[Nawaphan Watanasirisuk 3B]

Is it possible to ever have a negative oxidation number? If so how would that be reflected in the name because there is no +/- sign in the brackets

[Nancy Hu - 4E]

Is it possible to ever have a negative oxidation number? If so how would that be reflected in the name because there is no +/- sign in the brackets

Yes it is possible to have a negative oxidation number. To show that it is an anion, you would add -ate at the end of the central atom's name, and its Latin name will be used if it has one.