- A molecule is made up of two or more atoms that are chemically bonded together. Atoms are the fundamental particles, or elements, in nature. As of January 2008, the periodic table of elements listed 117 standard elements. However, additional "non-standard" elements have been discovered.
Molecules can be formed by atoms of the same element or of different elements, as in the case of H(2)O (water), which is two atoms hydrogen, one atom oxygen. The bond between atoms is selective; only certain types of atoms will attract and bond with each other. The variety of shapes and sizes of atoms determines what will attract what.
The investigation of molecules began as early as 450 B.C., when Greek philosophers Leucippus and Empedocles proposed ideas on the composition of all matter. Leucippus believed atoms and voids to be the components of matter, whereas Empedocles claimed that forces of attraction and repulsion existed between the basic elements air, water, fire and earth. Empedocles' theory prevailed, until the 1800s when scientists such as Isaac Newton, Rene Descartes and Pierre Gassendi began to re-explore the implications of Leucippus' atomic theory concept.
Robert T. Boyles was the first to mention a bonding force taking place between atoms, in his book "The Sceptical Chymist," written in 1661. Boyles described matter as made up of particle clusters that arranged and re-arranged themselves in groups. It wasn't until 1811 that Amedeo Avogadro introduced the idea of atoms forming into molecules in an essay entitled "Essay on Determining the Relative Masses of the Elementary Molecules of Bodies."- Atoms are made up of three subatomic particle types: protons, electrons and neutrons. Protons carry a positive charge, while electrons carry a negative one. Neutrons are neutral. Protons and electrons appear in equal amounts within each atom, which creates a neutral, or stable, electrical charge per atom. Molecules form when electrons are shared, or exchanged between atoms.
For structural reasons, only certain atoms will share electrons with certain other atoms. Atomic structure always sees protons and neutrons located at the center of the atom, while electrons reside in shell orbits of varying distances from the nucleus. The electrons in the outermost orbits of the atom join with other atoms' outlying electrons. - When atoms combine to form a molecule, a chemical bond is formed. This bond is typically one of two types: ionic or covalent.
The orbits in which the electrons reside can hold up to eight electrons a piece, except for the shell closest to the nucleus. This one can only hold two. The size, or weight, of the atom determines how many protons, neutrons and electrons it has. Atoms whose outer shells hold eight electrons are stable atoms. Those with fewer than eight electrons are less stable.
Ionic bonding happens when an atom attempts to stabilize its outer shell by taking an electron from another atom. When this happens, the atoms become ionized. That is, they take on a positive or negative charge because of the added or missing electrons. The atom that loses its electron will become positively charged, while the one that gained an electron becomes negatively charged. The two atoms bond as a result of their opposite charges.
Covalent bonds are a little different. Instead of one atom giving up its electrons to another, stray electrons are shared between the two atoms. This makes for a much stronger bond than the ionic molecule.
The study of molecular formations has taken a new slant in recent years. Scientists are working more closely with the subatomic properties of atoms and molecules to the extent of reconstructing these fundamental properties of our most basic elements. Nanotechnology---the study of molecular manufacturing---has emerged as the science of the future. Scientists within this field are learning how to work with the smallest pieces of matter, to recreate materials and systems on a micro-dimensional scale. Progress made within this field has the capability of revolutionizing our everyday lifestyles, specifically how we diagnose and treat disease, how we manufacture products, as well as our information processing abilities.
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