Why carbons form so many compounds

They can even be shared by other carbon atoms, which in turn can share electrons with other carbon atoms and so on, forming long strings of carbon atoms, bonded to each other like links in a chain.

Silicon Si , another element in group 14 of the periodic table, also has four valence electrons and can make large molecules called silicones, but its atoms are too large to fit together into as great a variety of molecules as carbon atoms can. Carbon's ability to form long carbon-to-carbon chains is the first of five reasons that there can be so many different carbon compounds; a molecule that differs by even one atom is, of course, a molecule of a different compound.

The second reason for carbon's astounding compound-forming ability is that carbon atoms can bind to each other not only in straight chains, but in complex branchings, like the branches of a tree. They can even join "head-to-tail" to make rings of carbon atoms. There is practically no limit to the number or complexity of the branches or the number of rings that can be attached to them, and hence no limit to the number of different molecules that can be formed.

The third reason is that carbon atoms can share not only a single electron with another atom to form a single bond, but it can also share two or three electrons, forming a double or triple bond. This makes for a huge number of possible bond combinations at different places, making a huge number of different possible molecules.

And a molecule that differs by even one atom or one bond position is a molecule of a different compound. The fourth reason is that the same collection of atoms and bonds, but in a different geometrical arrangement within the molecule, makes a molecule with a different shape and hence different properties.

These different molecules are called isomers. This dramatically increases the number of patterns that carbon atoms can make. Carbon can also link together in long chains or rings, carbon to carbon to carbon to carbon and so on. Chemists call these links chemical bonds; very long chains, made by joining short ones, are called polymers.

And, quite unusually, these long chains cannot be destroyed by water or air or be attacked by bacteria. This explains why so many plastics do not disintegrate in the environment in the way that other materials do. Only sunlight can destroy some polymers, causing the chains to break, and the material to become brittle. Carbon is part of many compounds, all of which have certain common properties. For example: 1 Few carbon based-compounds change quickly at ordinary temperatures, but they begin to react fiercely at high temperatures as in burning.

When they burn, the compound is oxidised and carbon dioxide is produced.