Your best friend in any chemistry course will always be The Periodic Table Of The Elements. This is a compact listing of many properties of the elements. Properties that are not explicitly noted can be remembered from chemistry concepts and an element's position on the table. The purpose of this page is to present a very short set of reminder-notes about the table and how to "navigate" it.
The whole basis for the word "periodic" in the name is the fact that elements of different weights and appearances have similar patterns of reactivities and physical properties. So if the elements are listed in order of increasing atomic number, there will be a pattern (or trend) to some property like first ionization energy. And every once in a while there will be an unreactive gas with a very high first ionization energy, followed by a soft metal with an extremely low one. Since this pattern repeats, it is called "periodic."
On The Web
First of all, there are many really cool Periodic Table web sites on the internet. On this site, I have three Excel 2000 files: the first one is just a bunch of periodic tables that I have formatted for various uses in class, and the second one is a spreadsheet with a whole bunch of data compiled about each element, and graphical representations of their trends. The third one was developed by a student named David Mack from an idea I had, and it shows the same data as the second one above, but the graphs are 3-D surface maps of the elements' properties drawn on a rotatable periodic table. It's pretty cool, so check it out (and e-mail me if you are super good with programming, because there are still some features I would like to add). There is a periodic table on this site that I will mention and link to later.
Also, there are many many many periodic table web-sites on the internet. Here are the six best that I have found since I started looking. Check them out; they are each interesting for different reasons.
The Layout Of The Table
Most periodic tables are set up the same way: seven rows (also called periods, numbered 1-7 so far) and 18 columns (also called groups, numbered 1-18), with two "orphaned" rows floating around the bottom of the page. Close examination of the sequence of atomic numbers will reveal that those bottom two rows could belong up in the body of the periodic table, sort of squeezed in under scandium and yttrium. One problem is that this would give the page unpleasant proportions [GOLDEN RATIO LINK HERE], so we pull them down and out. The man responsible for the realization that there is a good chemical reason for this was named Glenn Seaborg, and he now has an element named for him (#106, Seaborgium). LINK TO NON-TRADITIONAL SET-UP TABLES HERE.
There is also usually a bold zig-zag line running from just left of boron (#5) to the lower right hand corner of the table. Some people think this line looks like a staircase, so the scientific community calls it the staircase. This line separates elements that have been observed to be metals from those that have been observed to be non-metals. Elements touching the staircase often have some properties of both metals and non-metals, so they are called semi-metals or metalloids. [Note that if one continues the staircase beyond its present length, it will run off the table entirely. This means that there is only one more non-metal to be discovered - element #118. There have been reports that element 118 has already been discovered, but these are under some dispute, and it does not yet have a permanent name. Also, this element will be extremely radioactive and unstable, and it is unlikely that large amounts will ever be collected. It would be interesting to do so, however, because this last "noble gas" will likely be the rebel of its family, undergoing chemical reactions with relative ease, and being a liquid. Perhaps the name should be Rebellium?].
Metals are elements that have been observed to have certain properties in common. The most familiar of these are that they are malleable (they can be hammered into a sheet), ductile (they can be drawn into a wire), and they have an interesting reflective quality called luster. You can think of luster as the difference between gold and the color yellow. Also, metals are good conductors of heat and electricity, and they tend to lose electrons to become positive ions.
Non-Metals have pretty much the opposite properties of metals. They are brittle or gaseous, they are dull and non-reflective, they are often poor conductors of heat and electricity, and they tend to form negative ions. The staircase is drawn to touch the squares of elements with properties of both metals and non-metals.
Many periodic tables are printed in color, with the colors used to indicate whether an element is solid, liquid, or gas in it's standard state (298 K and 1 atm). Usually, elements written in black are solids, elements written in blue are liquids, and elements written in red are gases (although the large one from Flinn Scientific uses green for gases for some reason). There are only two liquid elements (so far), and most chemists remember which ones they are and which ones are gases, so black and white tables aren't too much of a problem. Elements that are shaded or outlined are synthetic and not found in nature. When a synthetic element is eventually found that is liquid or gaseous under standard conditions, I do not know if the outline will be blue or red.
Back in the day, I wrote a program in GW-Basic that would display the periodic table at various temperatures. For some reason, it runs more slowly on my 1.6 GHz laptop than it did on my 386-33MHz desktop, but it still works. You can see the solid/liquid/gas distribution at any temperature up to 10000 K, or watch how the distribution changes as temperature changes. Click here to get the program to run off your your hard drive, and click here to view the read-me file.
The elements on the periodic table are arranged in order of increasing atomic number, and elements with similar properties are placed in the same columns. Since elements are grouped according to similar properties or traits, these groupings are called families. They are often columns of elements, but not always. Here are the 11 families we will refer to in chemistry class.
|alkali metals||Most of the first column, from lithium down to francium.|
|alkaline earths||The second column, from beryllium down to radium.|
|transition metals||Everything from scandium to zinc and below. [Some people consider the transition metals to include the other metals to the right also, but we will not do that this year.]|
|boron family||Boron down to thallium (so far).|
|carbon family||Carbon down to lead (so far).|
|nitrogen family||Nitrogen down to bismuth (so far). Also called the "pnictides."|
|chalcogens||Oxygen down to polonium (so far). The name means "chalk-makers."|
|halogens||Fluorine down to astatine (so far). The name means "salt-makers."|
|noble gases||Helium down to radon (so far).|
|rare earth elements||The bottom two rows below the main body of the table.|
|hydrogen||Just hydrogen, by itself.|
Element names come from a wide variety of sources, and their symbols come from their names (or their old names). The symbols are usually one or two letters long, with the first one always capitalized and the second one always lowercase. A few elements have only one letter for the symbol, and this letter must always be capitalized. Discovery of brand new elements is often disputed, and temporary names are assigned by IUPAC (the International Union of Pure and Applied Chemists) until final agreement is reached on discovery and a name. The temporary names are always three letters long, with only the first capitalized. The letters stand for the latin prefix for each digit of the atomic number. For example, seaborgium, element 106, used to be called unnilhexium (un-nil-hex for 106).
Here is a site with the elements' names in Esperanto, the universal language of brotherhood and peace. I am really not kidding, and it is a pretty cool idea.
The other most useful piece of immediate information that the periodic table reveals has to do with the arrangement of electrons in an atom. Each new row on the periodic table correspnds with a new layer of electrons in the atoms. Hydrogen and helium only have one layer or electrons, while all the elements in the row with potassium have four layers of electrons.
The electrons in the outermost layer are special, because they are the ones involved in almost all chemical reaction. These are called valence electrons. The very first layer can only old two of them, but every other layer can hold eight. When the valence layer is full, further electrons must be stored in higher layers. Full layers are very stable for several reasons, so atoms tend to react until their valence level is either empty (metals) or full (non-metals). The number of valence electrons a neutral atom has is shown by the Roman numeral at the top of each column. (The only exception to this rule is helium, which is in column VIII even though it only has two valence electrons. It belongs in this column because it is the column of elements with full valence layers.)
[MHS Chem page]