Understanding the Periodic Table of the Elements

When a layperson hears the term, Periodic Table of the Elements their geek filter is activated. However, when they see the elaborate chart, a chemical game of Spider Solitaire may come to mind. However, for the trained eye, the Periodic Table is a using and wonderful organizational chart that helps a person understand the nature and characteristics of atoms and elemental groups.

The Earlier History of the Periodic Table of the Elements

In 1789, French chemist Antoine Lavoiser, after working on the law of conservation of mass, published a list of the 33 known chemical elements. His attempt led him to organize the elements in groups of gases, non-metals, metals, and Earth. The arrangement was enlightening, but still not wholly functional. As a result, scientists continued to search for amore accurate way to organize and classify the elements.

By the 1830s, German chemist Johann Dobereiner sought to group in triads and German chemist Leopold Gmelin following up with Doberiener's work, defined several triads. But, this system did not fully explain chemical reactions. Almost a decade later, Jean Baptist Dumas gleaned that certain elements, especially metals, had unique chemical relationships. By 1864, Julius Lothar Meyer, a German chemist, published an expanded list of 49 chemical elements. His organizational structure focused on what was known to him as valency, which is the number of chemical bonds formed by an atom. It was Meyer who seemed to be on the right track, but his method of organization did not fully explain other chemical characteristics of certain elements. In that same year, Englishman John Newlands attempted to classify elements by their atomic weight (with carbon being the standard.) Like Dobereiner, Newlands thought elements could be grouped in finite sets. He called his sets octaves as he thought the chemical and physical properties recurred in intervals of eight.

The Work of Mendeleev

Russian chemistry professor Dmitri Mendeleev, working independently of Meyer, published his periodic tables in 1869. In organizing the elements, he set them out in columns and rows. His attempted grouped elements based on chemical properties. In setting up his elemental organizational chart, Mendeleev created gaps for undiscovered chemical elements, which actually served to predict the existence of the existence of still more elements. Mendeleev's chart also served to group elements into chemical families based on characteristics. At the time his chart as published, Mendeleev had organized 65 known elements by atomic weight from left to right. His chart was intuitive and informative.

Parts of the Table

Nomenclature

Each element is represented on the Periodic table by a unique series of letters. An element can have one to three letters in its name. The elements listed in increasing atomic number order. The atomic number represents the number of protons in the nucleus or the electrons orbiting the nucleus. Helium has an atomic number of 2, which means that it has two protons in its nucleus or two electrons orbiting the nuclear core.

Groups

Groups are noted by the vertical column and are families of elements. The named groups include non-metals, noble gases (to which Helium includes), halogens, other metals, transitional elements, inner transitional elements, alkali metals, and alkaline earth metals.

These groups, which there are 18, consists of the elements have similar chemical and physical properties. For example, Group 18 consists of the noble gases - Helium, Neon, Argon, Radon, Ununoctium, Krypton and Xenon. These elements have low melting and boiling points, and they each are colorless, odorless, tasteless, and nonflammable. This group is known for its low chemical reactivity.

Periods

Periods are noted by the horizontal rows on the periodic chart. Each element in a period row tends to have the same number of electron orbits. Based on what man knows about the existing elements, seven is the maximum number of orbits and element can have.

The periodic chart has 7 periods. Elements such as Hydrogen and Helium are in Period 1- meaning they have one electron orbit. Elements such as Sodium and Magnesium, Aluminum, Potassium and Chlorine are in Period 3- meaning they have there electron orbits.

Blocks

While groups and periods are useful in understanding the chemical families, elements are also seen as being organized by blocks. There are 4 blocks (s, d, p and f) and blocks represent the subshell in which the last electron of the element resides. This pairing relates to atomic orbit type. The s block family includes hydrogen, helium, the alkali metals and the alkaline earth metals. Basically, the s block has Groups 1 and 2. The d block family consists of groups 3 to 12 while the p block holds have groups 13 through 18. The f block holds the rare earth metals which include the Lanthanoids. Over time, a g block may be added to represent the adding of an 8^th and 9^th period.

Colors

Over time a color scheme has been added to the periodic chart to help discern which elements belong to named categories. Charts vary, but most link elements in these categories Alkali metals, Alkaline earth metals, Inner Transitional, Lantanoids and Actinoids, Transitional, Metals, Metalloids, Halogens Other nonmetals, and Noble Gases.

How to Use the Table

Knowing the lay out of the periodic table helps. Reading the table from left to right or from top to bottom, a viewer will see the groupings and relationships of the elements.

In reviewing the information on each element, you will see that the symbol, atomic number and atomic mass. The symbol will be used to denote the element in chemical equations. The atomic number will let you know the number or protons (or electrons) in the element. And, the atomic mass will give you a clue as to the average mass of the element. This mass takes into account isotopes of the elements.

Using the subshell groupings and the periods, a student or chemist can predict an elements stability, boiling point and level of conductivity. They can predict properties such as stability, boiling point, and conductivity

118 elements strong, the Periodic Table of the Elements is a useful tool in evaluating the nature of elements and predicting chemical reactions. It is one of the most useful tools in chemistry and physics. The history of the chart and its use will continue to evolve as more elements are discovered and subatomic properties are explored.

For more information on the Periodic Table of Elements, you can go to your local library, chemistry teacher, or book store. Also, the Internet has several useful resources, which include:

http://periodic.lanl.gov/use.html

http://periodic.lanl.gov/default.htm

http://chemistry.about.com/library/blperiodictable.htm

http://www.wou.edu/las/physci/ch412/perhist.htmhttp://www.colorado.edu/physics/2000/periodic_table/index.html