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Oxide is a chemical compound that contains at least an oxygen atom and at least one other element. Most of the earth's crust consists of oxides. Oxides are formed when the elements oxidized by oxygen in the air. Burning hydrocarbons produces two major oxides of carbon, carbon monoxide, and carbon dioxide. Even material that is regarded as a pure element was often containing oxide sheath. For example, aluminum foil has a thin skin of Al2O3 that protects foil from corrosion. Oxides of Period 3 elements:

Na2O MgO Al2O3 SiO2 P4O10 SO2 SO3 P4O6 Cl2O7 Cl2O

Oxides of the first row is known as the highest oxides of each element. These oxides is one in which the elements of Period 3 is the highest oxidation state. In these oxides, all the outer electrons are involved in bond formation from sodium which has only one outer electron to chlorine with 7 outer electrons.


Trends in the structure of the metal oxide is contained giant ionic structure on the left of the period, giant covalent oxide (silicon dioskida) in the middle and on the right molecular oxides period.

Melting and boiling points

Giant structure (metal oxides and silicon dioxide) have high melting and boiling points are high because it takes energy to break the strong bond (ionic or covalent) working in three dimensions.

Oxides of phosphorus, sulfur and chlorine consists of individual molecules, some of which are small and simple, and the other in the form of polymers.

Attractive forces between these molecules in the form of dispersion / spread of van der Waals and dipole-dipole interactions. Varying size depends on the size, shape and polarity of each molecule, but it will always be weaker than needed to break the bond ionic or covalent giant structure.

Oxides tend to be gases, liquids or solids with low melting point.

Electric current conductivity

None of these oxides that have electrons that can move freely or. This means that none of these oxides that can conduct electric current in the solid state.

These oxides can undergo electrolysis when molten. Oxides can conduct electricity due to the movement of ions toward the electrode and the discharge of the ions when it reaches the electrode.

Metal oxides


Oxides of sodium, magnesium and aluminum consist of giant structures containing metal ions and oxide ions. Magnesium oxide has a structure like NaCl. Two others have more complicated structures that are beyond the scope of the syllabus at this level.

Melting and boiling points

There is a strong attractive forces between the ions of each oxide and attractive forces requires energy to be decided. Therefore, these oxides have high melting and boiling points higher.

Electric current conductivity

None of the metal oxides period of 3 to conduct electric current in the solid state, but electrolysis may be performed if thawed. The liquid can conduct electric current due to the movement and changes the charge of the ions that exist.

An example is the electrolysis of aluminum oxide is important in the manufacture of aluminum. Whether we can electrolyzing sodium oxide liquid depends on the fluid / discharge if sublimes or decomposes on normal condition or not. If sublimes, it will not be obtained for electrolysed fluid.

Magnesium and aluminum oxide has a very high melting point making it difficult to electrolysed in a simple laboratory.

Silicon dioxide (silicon (IV) oxide)


Electronegativity / electronegativity of elements increases during the period from left to right, and on silicon, electronegativity difference between silicon and oxygen are not large enough to form ionic bonds. Silicon dioxide has giant covalent structure ..

There are three different forms of silicon dioxide. The most memorable and described is a diamond-like structure.

Crystalline silicon has a structure similar to diamond. To turn it into silicon dioxide, silicon structural changes need to be done by inserting a few atoms of oxygen.

Note that each silicon atom with neighboring silicon atoms bridged by oxygen atoms. Do not forget that this is only a small part of giant structures in three dimensions.

Melting and boiling points

Silicon dioxide has a high melting point, vary depending on the structure (remember that only one of three possible structures), but the number was around 1700 ° C. Silicon-oxygen covalent bonds are very strong to be decided before melting. Silicon dioxide boils at 2230 ° C.

Since we are talking about the difference in the bond, did not mean to compare this value with other metal oxides. Better stated that because of the metal oxide and silicon dioxide has a giant structure, the melting point and high boiling point.

Electric current conductivity

Silicon dioxide has no electrons or ions can move so it can not conduct electricity, both in the solid state and liquid.

Oxide molecular

Phosphorus, sulfur and chlorine are all formed oxides composed of molecules. Some of these molecules are simple and other polymers. We will only discuss the simple molecules.

Melting and boiling points of these oxides will be lower than the metal oxide and silicon dioxide. Intermolecular forces binding the molecules with other molecules through van der Waals dispersion or dipole-dipole interactions. Its strength vary depending on the size of the molecule.

None of these oxides that conduct electricity either as a solid or liquid. None of which contain ions or free electrons.

Oxides of phosphorus

Phosphorus has two common oxides, phosphorus (III) oxide, P4O6, and phosphorus (V) oxide, P4O10.

Phosphorus (III) oxide

Phosphorus (III) oxide is a white solid, melting at 24 ° C and boils at 173 ° C.

The structure of the molecule is best composed of molecules that tetrahedral P4.

Pull this section so that we will see bond ....

Ties ... and then replace them with new bonds that connect atoms of phosphorus with oxygen atoms. It will form a V as in water, but will not be blamed if drawing a straight line between the phosphorus atoms, such as the example

Phosphorus use only three outer electrons (3 electrons unpaired p) form a triple bond with oxygen.

Phosphorus (V) oxide

Phosphorus (V) oxide is also a white solid to sublime (change from solid to gas) at 300 ° C. In this case, phosphorus use all outer electrons for bonding.

The solid phosphorus (V) oxide is in several different forms, some of which form the polymer. We will discuss a simple molecular form and is also located in a gaseous state.

This is easily illustrated by drawing P4O6 first. The other four oxygen atoms attached to the phosphorus atom through four bond.

Oxides of sulfur

Sulfur forms two common oxides, sulfur dioxide (sulfur (IV) oxide), SO2, and sulfur trioxide (sulfur (VI) oxide), SO3.

Sulfur dioxide

Sulfur dioxide is a colorless gas at room temperature are easily recognized by the distinctive odor / strangle. It consists of a simple molecular SO2.

Sulfur use four outer electrons to form a bond with oxygen, leaving two unpaired electrons on the sulfur. SO2 is the bent shape of the result of this lone pair.

Sulfur trioxide

Sulfur trioxide is pure white solid with a melting point and a low boiling point. Sulfur trioxide reacts rapidly with water vapor in the air to form sulfuric acid. This means that if we make it in the laboratory, it will appear as a solid with smoke in the air (to form sulfuric acid mist).

Sulfur trioxide in a gaseous state, consisting of simple molecules SO3 in which all the outer electrons of sulfur are involved in bond formation.

There are various forms sulfut trioxide. The simplest is a trimer, S3O9, where 3 SO3 molecules combine to form a ring.

There are other forms in which the polymer molecules SO3 combine to form a long chain. For example:

In fact the simple molecules joined in this way forming larger structures form a solid SO3

Chlorine oxide

Chlorine forms several oxides. Here we only discuss two of which are chlorine (I) oxide, Cl2O and chlorine (VII) oxide, Cl2O7.

Chlorine (I) oxide

Chlorine (I) oxide is colored yellowish gas at room temperature. It consists of a simple ionic molecules.

There is nothing surprising about this molecule and its physical properties only estimates of the size of the molecule.

Chlorine (VII) oxide

In the chlorine (VII) oxide, chlorine use 7 outer electrons to form a bond with oxygen. This produces larger molecules that can be estimated that the melting point and boiling point higher than that of chlorine (I) oxide.

Chlorine (VII) oxide is a liquid as a colorless oil at room temperature.

In the diagram, the structure of the standard formula portrayed. In fact, the shape is tetrahedral around both Cl and V-shaped around the central oxygen.

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