Thursday, February 11, 2016

Chemistry for Preppers: Elements

I've thought about starting a series of articles covering “Chemistry for Preppers” for a long time, and this is the first of a potentially long series. The depth of information will be determined by the feedback I receive from the readers and my fellow authors. If you didn't take or don't remember high school chemistry, a lot of this will be new information, but anyone with college-level chemistry will find it fairly basic. I am going to gloss over a lot of quibbles and minute details unless I am asked to be more precise; this is basic chemistry, after all, not Organic or Physical Chemistry. The first few articles will be basic chemistry with applied chemistry to follow.

If you're interested in having an excellent reference book on your shelf, I strongly suggest the CRC (Chemical Rubber Company) Handbook of Chemistry and Physics. They're up to the 96th edition and they are expensive, but the information in them changes so slowly and in such small amounts that any edition you can find will suffice, so look in used book stores or second-hand shops around colleges for a cheap copy. You can find a lot of the history of each element in the Handbook, along with more data than most of us will ever need.

A Little History
The study of what things are made of started with the ancient alchemists, who were searching for ways to transmute (change) cheap, common materials into expensive, rare materials. In their search, they found that there were many different kinds of “elemental” materials that couldn't be broken down into anything simpler. These became the basic elements, and were organized into a table (see below) by how they acted and reacted, which led to the deduction that there were holes in the table and therefore undiscovered elements. Chemists searched for these “missing” elements for centuries, often competing with each other to be the first to isolate a rare or stubborn element.

Periodic Table
Everyone has seen the Periodic table of the Elements, but how many of you know how to read the information that's in it? A good table will give name, symbol, number, atomic weight, and sometimes other information.

There are 92 naturally-occurring elements and 26 man-made elements. The man-made elements tend to be very radioactive and decay rapidly, normally small fractions of a second. The natural elements have names and symbols that are relics of the alchemists and the various languages spoken by the people who first isolated them. The man-made elements are often named after prominent physicists and physics labs. Some of the newer elements don't have official names and are referred to by their atomic number (in Latin) followed by the common -ium suffix.

The vertical columns are called Groups, and the horizontal rows are called Periods. 
  • Groups share physical characteristics, with activity generally higher at the top and declining as you go down through the Group. 
    • Hydrogen is in a Group by itself, having no neutrons in the most common isotope.
    • Alkali Metals react with water, stripping the oxygen away from the hydrogen and generating heat. 
    • Alkaline Earths are soft metals that also react with water. 
    • Metals, Transition Metals, and Semimetals are mostly solids that conduct electricity. 
      • Transition refers to electron behavior, and not the quality of metal. 
      • Semimetals are sometimes conductors and sometimes insulators, hence the "semi". 
    • Nonmetals are normally found tied to other elements, such as Oxygen to Nitrogen or Hydrogen. 
    • Halogens are very reactive, but Noble Gasses are completely inert and won't react with anything. 
    • Lanthanides are known as the “rare earths” because they are not very common in the Earth's crust. 
    • Actinides consist of naturally radioactive elements that decay through the release of atomic radiation (alpha, beta, gamma) to isotopes of lower elements.
  • Periods are set by the configuration of the electrons in the various shells around the atomic nucleus. The innermost shell will only hold two electrons, The second and third can hold 8 electrons each, the fourth and fifth each hold 18, the sixth and seventh each hold 32.
Positive, Negative, Neutral
All matter is made of three basic atomic particles (sub-atomic particles are above my pay-grade).
  • Protons are positively charged particles in the nucleus of the atom. The number of protons is the atomic number of the element. Since positive charges attract negative charges, there are generally an equal number of protons and electrons.
  • Neutrons are neutral (non-charged) particles in the nucleus that weigh as much as protons. The number of neutrons added to the number of protons equals the atomic weight or atomic mass of an element. The number of neutrons can vary without changing the element, and these variations are known as isotopes of the element. The atomic mass of an element is usually given as an average of all naturally-occurring isotopes for an element, and is rarely a whole number.
  • Electrons are negatively-charged particles that orbit the nucleus of the atom in distinct shells. Electrons have negligible weight and don't influence the atomic weight of an element. Electrons often move from atom to atom, and any time there is a difference in the number of protons and electrons, the atom is deemed an ion.

That covers elements. Next week I'll start putting a few of them together and we'll cover molecules and atomic bonds. If I can find decent graphics I will use them; otherwise, you may be forced to suffer through my attempts to use MS Paint or something similar.

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