Can some nice chemist explain to me the system of naming compounds with roman numerals? Also while they are here, tell me exactly the difference between molecules and compounds. Thanks!
a compound has as its fundamental unit (that cannot be subdivided without changing chemical characterists)a molecule. For instance, C6H12O5 is the formula for the molecule of sugar. If many of these molecules are grouped together, we call that grouping a chemical compound. In history, there were atoms proposed as the fundamental unit of elements, and compound atoms were the fundamental elements of chemical compounds. Over the past 150 years, we have altered the definitions slightly.
The naming system inserts into a chemical name its valence state, if it is multivalent element.
For instance CuO is no longer cupric oxide, we name it Copper(II) oxide. Many folks still hang on to the -ic; -ous, hypo -ous latin suffics/prefixes.
Cu2O is Copper(I) oxide, no longer Cuprous oxide.
Ferric becomes Iron(III)
Ferrous becomes Iron (II)
Where this new system is of great advantage, is in metals which have more than two valences. We now can easily name compounds with
Manganese(I)
Manganese(II)
Manganese(III) and so on through Manganese(VII)
Now why Roman Numerals? Why not Arabic Numerals. That is a really good question. The answer lies in history and how history leads to symbols, and our ties to the Romans, I guess.
Bob,
I believe roman numerals were chosen to avoid potential confusion with Arabic Numerals which are used to indicate composition. As you say they have been used historically to indicate oxidation state.
Certainly! I can explain both the system of naming compounds with Roman numerals and the difference between molecules and compounds.
1. Naming Compounds with Roman Numerals:
When it comes to naming compounds, Roman numerals are often used to indicate the oxidation state or charge of an element within the compound. This is particularly useful for transition metals that can exhibit multiple oxidation states.
To apply Roman numerals in compound names, you need to determine the charge of the metal ion. It is not always obvious, so you should look at the compound's formula or consider the overall charge of the compound.
For example, let's consider the compound FeCl2. Iron (Fe) is a transition metal that can have multiple oxidation states. In this case, we can determine the oxidation state of iron based on the charge of the chloride ion (Cl-) since it is known that chlorides have a charge of -1. Since there are two chloride ions in the formula, the overall charge is -2. Therefore, the iron ion (Fe) must have an oxidation state of +2 to balance the overall charge. Consequently, the compound is named Iron(II) chloride.
It is important to note that not all compounds require Roman numerals in their names. Roman numerals are only used when naming transition metal compounds where the metal can have more than one oxidation state.
2. Difference between Molecules and Compounds:
Molecules and compounds are both forms of chemical substances but with some distinction in their definitions.
A molecule is a collection of two or more atoms held together by chemical bonds. These atoms can be of the same element or different elements. Molecules can be either pure elements (such as oxygen gas, O2) or compounds (such as water, H2O). Molecules exist as discrete, separate entities.
On the other hand, a compound is a substance composed of two or more different elements chemically combined in fixed ratios. Compounds are formed when atoms of different elements bond together chemically. For instance, water (H2O) is a compound because it contains atoms of two different elements, hydrogen and oxygen, combined in a fixed ratio.
To summarize, molecules can be substances that consist of either a single element or multiple different elements, whereas compounds specifically refer to substances composed of atoms of different elements chemically bonded together.
I hope this explanation clarifies the naming of compounds with Roman numerals and the difference between molecules and compounds. Let me know if there is anything else I can help you with!