The Alphabet of Chemistry


Combinations of 26 letters make up every word in the English language, 28 in the case of Arabic. Similarly, every material in the world is composed of different combinations of about 100 elements that cannot be broken down into simpler substances through ordinary chemistry.

We may never be able to attribute the development of the basic building blocks of writing, the Alphabet, to one single individual. We do know, however, the man who devised the method for classifying the basic building blocks of matter, which we know as the Periodic Table of Elements.

Russian chemist Dmitri Mendeleev (1834-1907) is the one who, in 1869, proposed that all chemical elements exhibit a "periodicity of properties". As a result, he tried to organize the chemical elements according to their atomic weights, known to be roughly equal to the number of protons plus neutrons in the nucleus, assuming that the properties of the elements would gradually change as atomic weight increased.

What he found, however, was that the chemical properties of the elements increased gradually and then suddenly changed at distinct steps, or periods as he called them. To account for these repeating trends, Mendeleev grouped the elements in a table that had both rows, or periods, and columns, or groups.

The modern periodic table of elements is based on Mendeleev's observations. However, instead of being organized by atomic weight, the modern table is arranged by atomic number, which is known as the number of protons inside the nucleus. As one moves from left to right in a row of the periodic table, the properties of the elements gradually change. At the end of each row, a drastic shift occurs in the chemical properties. The next element in order of atomic number is more similar, chemically speaking, to the first element in the row above it; thus a new row begins on the table.

Groups of the periodic table are the eighteen series of elements in columns across the table, each of these groups are special for the common characteristics their constituent elements share. Elements in a given group in the periodic table share many similar chemical properties.

Known as alkali metals, Group 1A elements are never found free in nature; they react with H2O to form alkaline (basic) solutions. On the other hand, Group 2A elements are known as Alkaline Earth Metals; they react with oxygen in the general formula EO, where O is oxygen and E is a Group 2A element, to form basic solutions. Group 3A elements, known as Metalloids, react to form oxygen compounds with an X2O3 formula, where O is oxygen and X is a Group 3A element.

Group 4A includes metals and non-metals, going from non-metals at the top of the column to metals at the bottom. Group 5A elements on the other hand form an oxygen or sulfur compound with E2O3 or E2S3 formulas, where O is oxygen, S is sulfur and E is a Group 5A element.

One of the most abundant elements, oxygen is a Group 6A element. Generally, oxygen compound formulas within this group are EO2 and EO3, where O is oxygen and E is a Group 6A element. Halogens, meaning "salt-forming", are Group 7A elements; they are all highly reactive and combine violently with alkali metals to form salts. On the contrary, elements of Group 8A are noble gases that are not very reactive.

Transitions elements are found in groups 1B, 2B 3B, 4B, 5B, 6B, 7B, 8B, while Rare Earth Metals are found in Lanthanides series and Actinides series. As for Group 0, it contains inert gases; they are called so because their oxidation number of 0 prevents them from forming compounds readily.

In each period, or horizontal row, the atomic numbers increase from left to right. The periods are numbered 1 through 7 on the left-hand side of the table. Elements that are in the same period have chemical properties that are not all that similar.

Consider the first two members of period 3: sodium (Na) and magnesium (Mg). In reactions, they both tend to lose electrons, but sodium loses one electron, while magnesium loses two. Chlorine (Cl), down near the end of the period, tends to gain an electron.

The periodic table is considered to be a huge efficient resource for scientists, teachers and students among others. The periodic table describes the atomic structure of each element known to mankind, each with its own unique set of data. By looking at the periodic table, a person can find out how many electrons an element has and how much it weighs. If one is uncertain what a matter is, one can look at the atomic structure of the material, compare it to the information in the periodic table, and identify the material by matching it to the element on the table with the same data. Just like deciphering a code!


*Published in the PSC Newsletter, Spring 2011 Issue.

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