Molecules

                                  Molecules

A molecule is defined as a group of two or more atoms arranged in a precise arrangement by means of covalent bonds. A molecule can range in size from two atoms, for example, H 2 (hydrogen), to thousands of atoms in macromolecules such as proteins, nucleic acids or synthetic and natural polymers. It can also occur ionic bonds, hydrogen bonds and other types of chemical bonds between different parts of the molecule, but it is only covalent bonds that are always between atoms in the same molecule.Within the kinetic theory of gases often used the term molecule for all particles in gas regardless of its constituents. According to this definition include noble gases molecules even though they only consist of single unbound atoms. Proteins with quaternary structure consists in fact in many cases by more molecules held together by intermolecular forces, although biochemists often regard them as a single molecule.

                                      Bonding

For a molecule to exist, atoms have to stick together. This happens when two atoms share electrons. Instead of circling just one atom, the electron now circles around two. This is called bonding. The shared electrons are called 'bonds'. Sometimes, more than one electron is shared. The more electrons are shared, the stronger the bond gets and the stronger the atoms stick together. Bonds can also be broken apart. Since most bonds require energy to form, they also give off energy when they are broken. But before most bonds break, the molecule has to be heated. Then the atoms start to move, and when they move too much, the bond breaks. Molecules that require less energy to break than they give off when broken are called fuels. For example, a candle will just sit there and nothing happens. But when you use a match to light it, it will burn for a long time. The match brings the energy to break the first bonds, which release enough energy to break the bonds below them, until the candle has burned down.

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