Atoms Quarks Gluons and Isotopes

Ok…lets start in on atoms.

Atoms are small, but not so small as one may think. To put their size a little more in perspective, a human hair has a thickens of about 200,000 atoms. A human red blood cell has a diameter of about 10,000 atoms. Now those numbers may seem large, but you will notice they are not so large that they require scientific notation, they are actually manageable. So manageable in fact that in 1989 Donald Eigler a physicist at the IBM Almaden Research Center demonstrated the ability to work with individual atoms by writing the letters IBM with 35 individual xenon atoms.

Now although the atom itself is not unreasonably small, its constituent parts seem to be. An atom consists of a cloud of electrons that flutter about a tiny nucleus that is some 100,000 times smaller than the atom itself. To put that in perspective, if an atoms electron cloud was blown up to the size of an average football stadium its nucleus would be no larger then a mosquito at its center. Because of this many have felt that an atom is mostly empty space. In reality though this is only partly true, as that space is filled with cloud of very active electrons. Its also good to note that the long held analogy to describe an atoms structure as being like that of a small solar system, while attractive as a visual tool, is so far from reality that I believe it serves only to confuse rather then instruct. The idea of an infinitesimally small nucleus surrounded by a cloud or fog that represents the probable location of an electron is much more palatable. This can be emphasized by the fact that since an electrons location is only a probability there is a chance you may find the electron within the nucleus itself. This on occasion does happen and results in what is often called a K-Capture that allows an inner electron to be absorbed by a proton, changing it to a neutron, and as a byproduct emitting a neutrino. This is a fairly standard form of decay for isotopes that have an overabundance of protons in the nucleus. It is responsible for changing one element into another such as Potassium into Argon (useful forPotassium–argon dating) or Aluminum to Magnesium, or Nickel to Cobalt. This process would be quite impossible if the antiquated particle-centric model of a fixed orbit where anywhere near a reality.

In the nucleus the primary units are protons and neutrons. Protons have a mass of about 2000 times that of electrons and the same charge. Neutrons have a mass nearly equal to protons, but lack an electric charge so they are neutral.

From there things can be broken down further in some some-what confusing ways.

Protons, and neutrons are made up of particles named quarks, and their binding constituents called gluons that “glue” the quarks together. The quarks in protons and neutrons come in two forms, up and down quarks, and are distinguishable by their charge. Here is where things begin to get awkward. The quirky quarks where discovered by a man of a character befitting their colorful discovery, Murray Gell-Mann. (If one has the time and passion I suggest reading Gell-Manns book, “The Quark and the Jaguar”.) The true existence of these enigmatic particles was dodged and eschewed for some time due to their strange fractional charge. Up-type quarks have a +2/3 charge, while down-type quarks have a -1/3 charge. So when combined in the right way they allow for protons to have a whole charge of +1 (two up quarks +4/3 and one down quark -1/3) and neutrons to have no charge or 0 (two down quarks -2/3, and one up quark +2/3). The fun does not end there as these quarks are held together by gluons.

Gluons are even more mysterious and cross boundaries in physics and participate in as well as mediate interactions. To simplify though, gluons are the stuff that holds the quarks together. Unlike may other forces that have a strength that decreases with distance, quarks force increases with the distance stretched, much like if one stretches a rubber band. Because of these properties, gluons are typically confined within their composite particles. In the event enough energy is introduced to break a gluon free generally that very energy is enough to create another gluon in its place. Also interesting about gluons is one would think that since gluons are generally massless quarks would make up the bulk of a proton or neutrons mass. This though is not the case. Quarks make up a small fraction of the total mass of neutrons or protons, while the mass-energy of the gluon field that binds the quarks provides the lions share of the mass.

Finally one more item to consider in brief are isotopes. As we know atoms are composed of Protons, and Neutrons. In some elements there is a condition where there may be “extra” or “missing” neutrons. Although the chemical reaction of these elements are quite similar due to their similar number of electrons, extra or missing neutrons change the decay properties of the element, in some cases making it highly radioactive. A good example of this is uranium. Around 99% of uranium found naturally on the planet has a nucleus with some 92 protons, and 146 neutrons. This makes the total particles in the nucleus 238, thus the title U-238. A very small portion of naturally found uranium has only 143 neutrons. This isotope of uranium titled U-235 is very useful due to the decay properties and its relative instability, and is a key isotope in both nuclear weaponry, and the production of nuclear energy.