Chemistry Definitions: The Chemistry of Solar Part 2

Chemistry Definitions: Metals ans Non-Metals

Metals: These are elements that lose outer shell electrons to achieve a full outer shell. This results in an imbalance in the charge of the atom. A charged atom is are called an ion. Metal ions are positively charged; these are called cations. In metals, the cations and free electrons remain together, each held in place by the opposite charge of the other.

While not classed as a metal, the simplest cation is formed from Hydrogen, commonly encountered in the form of the Hydronium Ion. This is usually formed from the reaction of a strong acid such as Hydrochloric acid with water. For more information on acids and the pH scale have a look at this chemistry help site.


Non-Metals: These are elements that gain outer shell electrons to achieve a full outer shell. Since these atoms have picked up one or more extra electrons they have an overall negative charge. Negatively charged ions are called anions.


Chemistry Definitions: Three Types of Bonding

Technically, the type of bond between two elements is defined by their electronegativity values, though for the majority of elements that we experience in every day life we can simplify this by arranging the two groups, metals and non-metals, into three combinations:


Metal and metal: METALLIC BONDING. Metal atoms surrender their outer shell electrons to form stable positively charged ions. The positive ions are locked into layers by the presence of the free electrons, which are in turn retained by the charge of the ion layers. Find more metal information here.

Metal and non-metal: IONIC BONDING. This type of bonding works solely on the attraction of opposite charges, similar to how opposite ends of magnets stick together. Compounds formed in this way are called salts, the most familiar of which is sodium chloride, also known as table salt. Another example is sodium hydroxide, which is important in many areas including biodiesel production. These compounds are also called inorganic because they do not contain any carbon that is covalently bonded to other elements. Formulae for ionic compounds are merely ratios of the ingredients, such as NaCl, since there are no discreet molecules present.

Some ionic substances are able to harness sunlight to speed up or cause chamical reactions. Titanium Dioxide is an example of this, and when formed into nanotubes its effectiveness is greatly increased.

Non-metal and non-metal: COVALENT BONDING. Elements share electrons and are therefore joined to each other by that sharing. Compounds formed by covalent bonding are molecular, containing an exact number of atoms joined to each other. A good example of this is sugar, which is produced by plants using photosynthesis, nature's own solar power plant. Many bonds are not an equal sharing of electrons. We can use our knowledge of electronegativity values to predict when a polar covalent bond will occur.


These three combinations cover virtually all the types of bonding surrounding us, and each requires separate description if we are to get a clear picture of how solar panels take advantage of bonding and chemical structure to produce electricity. In order to gain maximum value from this, it is useful to understand the oxidation number rules as this aids our understanding of chemical reactions. Once we have this knowledge we are able to proceed to understanding balancing redox reactions that form the bulk of the chemistry involved in electricity production.


Chemistry Definitions: The Covalent Bonding of Carbon: A Special Investigation

The way that carbon atoms bond with each other and with other elements deserves special treatment. This is not only because it is fundamental to life on Earth, but also because by understanding the behaviour of Carbon we can gain great insight into the chemistry of the other elements involved in the successful operation of solar energy cells.

We have already seen that the element Carbon has four outer shell electrons and needs to have a total of eight to be stable. Since it can neither gain nor lose these electrons, it needs to share them with other elements.

This can be clearly seen in the formation of the chemical Methane, where Carbon combines with four Hydrogen atoms in order to gain 8 electrons in its outer shell. This is also true of Carbon in its interactions with any other elements, or indeed in its interactions with other Carbon atoms. It is this property that allows the many allotropes of pure Carbon to exist.

Chemistry Definitions: Building Carbon Chains

We can use the electron dot diagram of Carbon to construct molecules that are chains of Carbon atoms bonded to each other. The alkane series are a group of molecules made entirely from Carbon and Hydrogen. They are very simple molecules that allow us to master the basics of molecule model building. Once we have mastered the single bonded Carbon atoms, we can consider the alkene series which contain slightly more complex bonding. Once we understand this series, being able to construct the alkyne series is simple.