Atoms

At one level of inspection atoms are composed of three parts. protons, neutrons and electrons. These may be analyzed further yet but that is another level of study. Protons have a positive charge and are in the nucleus of the atom along with neutrons which have a neutral charge. Each of these particles have about the same weight. Electrons have a negative charge and reside in electron clouds about the nucleus. The protons and neutrons reside in the nucleus of the atom and thus are referred to as nucleons. The nucleons comprise most of the weight of the atom and the atomic weight of an atom can be rounded to the number of protons and neutrons in the nucleus. The atomic number of an atom is the number of protons and we can infer that there will be an equal number of electrons since the total charge in an atom must be zero. If an atom has greater or fewer number of electrons, it is either a negative ion or positive ion respectively. The weight of an electron is about 1/1837th the weight of a nucleon. The term for the weight of a nucleon is Atomic Mass Unit (AMU). It would take about 1,675,000,000,000,000,000,000,000 nucleons to weigh 1 gram.

The elecrtron can be analyzed in several ways. Presently, the Bohr model of the atom will be used which uses the shell model for evaluating electrons. The shell model has electrons residing in various energy levels about the nucleus. The first shell (K Shell) can have up to 2 electrons. This shell is filled first with electrons, thus any atom with greater than 2 protons or atomic number will have this shell filled. The next shell is the (L Shell) and can have up to 8 electrons in it. So on with the (M Shell). When the number of electrons starts filling the (N Shell) they then start packing in the inner shells with some more electrons as the VRML renderings of the atoms in the Periodic Table displays. The normal Bohr model of the atom would show the electron shells on a plane as similar to a solar system view, but the electron shells were shifted a bit to reflect a more 3 dimensional model.

It is the outermost shell of the atom which is used to analyze which atoms will Bond with each other. The outer shell has an electrical tendency to either fill or empty, thus it will have a tendency to lose its electrons completely or gain until it has 8 (except with Hydrogen and Helium it will lose its electron or gain until it has 2, since they have only electrons in the K Shell). It will give up, lend, borrow or steal electrons to do this. If an atom has 6 electrons in its outer shell (Oxygen), it will have more tendency to attract 2 electrons to make 8 than give up 6 to make 0 so it has 2 valence electrons. Valence electrons are the number of electrons of an atom that are involved in a chemical bond. The Oxidation Numbers of the atoms are a signed value of valence numbers that reflect the charge of the atom after the chemical bond. Thus the oxidation number of Oxygen is -2 because the atom will have more electrons associated with it after bonding with another atom or atoms.