Periodic Table of Elements
The Periodic Table of Elements is the most important reference in chemistry, and it represents all the known chemical elements as well as those that are yet to be discovered. The elements are arranged in a systematic order to show their patterned recurring or ‘periodic’ chemical and physiological properties. Currently, there are a total of 117 elements in the standard periodic chart.
The discovery of the individual elements led to the recognition of the similarities of their physical and chemical properties, and scientists soon found a way to organize them in a classification scheme. Dmitri Ivanovich Mendeleev, a Russian scientist, was credited as the first person to develop a schematic arrangement of these elements, and it became known as the Periodic Table.
During the 19th century, Mendeleev made studies to identify the properties of the elements, and he used the data to organize them according to certain patterns of similarities. To aid his studies, he made individual cards for each of the 63 known elements. Each card contained the symbol of an element, as well as its atomic weight, characteristic chemical, and physical properties. He then arranged the cards into a table in an order that showed the progressive values of their atomic masses, and he predicted the existence of other undiscovered elements, for which he left blank spaces on the table. From this draft table, the periodic law was formulated. In 1869, the first Periodic Table was published.
Below are examples of other precursors of the modern periodic table:
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LENNTECH - Periodic Table History: Shows the history of the periodic table of chemical elements
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AUS-e-TUTE - History of the Periodic Table of Elements: Lists the names of those who contributed to the development of the periodic table, and other significant data about the history of the periodic table.
The modern periodic table is divided into numerous groups, according to the similarities of the elements’ chemical properties, and these are shown in columns. The elements that appear in the same column belong to a family with similar reactive qualities. Below are the identified columns:
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Column I A: The Alkali Metals
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Column II A: The Alkaline Earths
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Columns III B – I B: Transition Elements
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Column 0: Noble Gases
When reading the periodic table, it is important to take note of the individual box that holds the basic information about each element in the columns. The Atomic Number that appears first represents the number of protons that are present in an atom, and it defines what the element is. Another thing to note is the Element Symbol, which is the letter or two that represents the element. Lastly, the Atomic Mass, which is the average mass of one atom expressed in atomic mass unit, or amu, is shown in decimal number. It represents the average of the isotopes of an element, since different isotopes of the same element have different masses.
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Dayah.com - Periodic Table: Provides a comprehensive guide to the elements in the periodic table
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PeriodicTable.com: Shows illustrations and links to all the known chemical elements
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Los Alamos National Laboratory’s Chemical Division - Table of the Elements: Features links for each element with information about the history, sources, properties, and others
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Visual Elements Periodic Table: Presents the periodic table in flash version with links to visual representations and information on the elements
The periodic table is essential for the understanding of the complexities of chemical elements, as well as their behaviors, reactions, and uses. It is widely used in chemistry, physics, biology, and chemical engineering. The table is also an easy guide for students who are studying chemistry and related subjects.
