Inorganic Reactions: Oxides Nomenclature

Oxides, in most industries this is the worst thing you could see, this is a sign of time taking its share out of metals.

But let’s take a look at our beloved elements first; to study oxides first we have to learn the oxidation numbers of some of the main elements.

At first it’s not mandatory for you to learn them all, but in the long term you should.

There are 2 main families of elements, the metals and the non metals families.

Oxygen form Oxides with metals and Anhydrides with non-metals (fancy way to say oxides of non-metals)

MONOVALENT				DIVALENT
Lithium Sodium Potassium Silver Rubidium Cesium Ion Ammonium Francium	Li Na K Ag Rb Cs NH4+ Fr	+1		Beryllium Magnesium Calcium Strontium Barium Radium Zinc Cadmium	Be Mg Ca Sr Ba Rd Zn Cd	+2
TRIVALENT				DI-TRIVALENT
Aluminum Bismuth	Al Bi	+3		Chromium Manganese Iron Cobalt Nickel	Cr Mn Fe Co Ni	+2 +3
MONO-DIVALENT				DI-TETRAVALENT
Copper Mercury	Cu Hg	+1 +2		Lead Tin Platinum Iridium Palladium	Pb Sn Pt Ir Pd	+2 +4
MONO-TRIVALENT
Gold	Au	+1 +3

Those numbers are the MOST COMMON oxidation states of elements, the oxidation state “measures the degree of oxidation of an atom in a substance” according to the IUPAC (International Union of Pure and Applied Chemistry)

The IUPAC has a set of rules for oxidation states, some of them are:

• The oxidation state of a free element (uncombined) is zero
• Hydrogen has an oxidation state of 1 and Oxygen has an oxidation state of -2 when they are present in most compounds. (Exceptions to this are that hydrogen has an oxidation state of -1 in hydrides of active metals, and oxygen has an oxidation state of -1 in peroxides)
• The algebraic sum of oxidation states of all atoms in a neutral molecule must be zero, while in ions the algebraic sum of the oxidation states of the constituent atoms must be equal to the charge on the ion.

OXIDATION AND REDUCTION

OXIDATION DOES NOT mean that the element has been exposed to oxygen. (Even if it sounds like it).

• OXIDATION: is the loss of electrons by a molecule, atom or ion. 

  

• REDUCTION: is the gain of electrons by a molecule, atom or ion.

In chemical reactions happens BOTH. If one element is being oxidized, the other is being reduced.

OXIDE FORMATION

Oxides are formed when the metal in its ground state is exposed to oxygen.

4 Al  +  3 O₂   ----->    2 Al₂O₃

In this reaction the element is oxidized and the oxygen reduced.

Al⁰  ------>  Al⁺³   Oxidation

O⁰   ------>  O^-2     Reduction

For teaching purposes you don’t need to know how to make the chemical reactions, but just the final compound.

Compound formulas have 2 main parts:

This is why I told you to learn the abbreviation and oxidation numbers of elements.

This is the correct way to write oxides.

[METAL]O

Now we just need to know how to figure out the subscript A,B of the atoms (the subscript tells us how many atoms of that element is present in that molecule)

[METAL]_AO_B

For OXIDES the oxygen always has an oxidation state of -2 (don’t forget this), and depending of the metal or non-metal there can be many options for compounds.

First you write the oxidation number:

Now you just have to SWITCH the numbers like this and you are done, know you know how to make oxides.

What about even oxidation numbers? You just have to simplify it if you can.

OXIDE/ANHYDRIDE NOMENCLATURE

Now that we know how to make the formulas of oxides, we have to know how to name then correctly.

There are 3 ways of naming oxides.

• TRADITIONAL nomenclature
• IUPAC nomenclature
• STOCK nomenclature

TRADITIONAL NOMENCLATURE

To name oxides according to the traditional nomenclature you need to learn a little system of prefixes and suffixes (for the oxidation numbers)

• If it only has 1 oxidation number there isn’t a suffix to use, some people use the –ic suffix.

• If it has 2

-ous	-ic
+2	+3
+1	+2

Note that the suffix does not depend on the number but on how many valences the element has. I’ve seen people making the mistake to think that +2 is always –ous or always –ic.

EXAMPLE

Name this oxide

Mn₂O₃

Remember how to make oxide formulas? Now we just need to go backwards to figure out which oxidation number the metal is using.

 Now that we know which it is, let’s find the correct suffix to use. It has 2 oxidation numbers:

+2 ----> -ous

+3 ----> -ic

Traditional nomenclature has this writing structure:

[ELEMENT NAME][SUFFIX] Oxide

So we just need to fill the name of the metal and the suffix

Manganic Oxide

Be careful with some element names, some aren’t use in nomenclature, such as IRON (Fe): so it wouldn’t be IRONIC OXIDE (heheh), but FERRIC OXIDE

IUPAC NOMENCLATURE

This one is the easiest in my opinion, it is also called “systematic”; you just need to learn these prefixes:

Number	Prefix
1	mono-
2	di-
3	tri-
4	tetra-
5	penta-
6	hexa-
7	hepta-
8	octa-
9	nona-
10	deca-

EXAMPLE:

Mn₂O₃

You just need to use the prefixes to name the element according of the subscripts.

In this case the structure of IUPAC nomenclature is

[PREFIX][ELEMENT NAME]  [PREFIX]Oxide

So this is the name of the oxide according to IUPAC Nomenclature:

diManganese triOxide

STOCK NOMENCLATURE

This is an easy nomenclature as well; you don’t have to know anything else but the oxidation numbers of the elements.

EXAMPLE:

Mn₂O₃

First step is to figure out the oxidation number of the metal:

 The structure of STOCK nomenclature is

[ELEMENT NAME][OX. NUMBER]     Oxide

The oxidation number of the metal has to be written in Roman numbers (I, II, III, IV, etc.).

This is the name according to Stock Nomenclature:

Manganese(III) Oxide

Be careful with writing a space between the name and the Roman number, there isn't one.

Coming Up!: Oxide Exercises