Periodic Table (Encyclopedia of Science)
The periodic table is a chart that shows the chemical elements and their relationship to each other. The periodic table is a graphic way of representing the periodic law.
History of the periodic law
By the middle of the nineteenth century, about 50 chemical elements were known. One of the questions chemists were asking about those elements was the following: Is every element entirely different from every other element? Or are some elements related to other elements in some way? Are there patterns among the elements?
A number of chemists suggested various patterns. German chemist Johann Wolfgang Döbereiner (1780849) observed in 1829, for example, that three of the so-called halogen elements (chlorine, bromine, and iodine) could be classified according to their atomic weights. The atomic weight of bromine (79.9) turned out to be almost the exact average of the atomic weights of chlorine (35.5) and iodine (127), with 35.5 + 127 ÷ 2 = 81.25 (almost 79.9)
Most of these classification schemes were not very successful. Then, in about 1869, two chemists made almost the same discovery at almost the same time. Russian chemist Dmitry Mendeleev (1834907) and German chemist Julius Lothar Meyer (1830895) suggested arranging the elements according to their atomic weights. In doing so, Mendeleev and Meyer pointed out, the properties...
(The entire section is 1073 words.)
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Periodic Table (Science Experiments)
Blocks of data
Soluble Families: How does the solubility of an element relate to where it is located on the Periodic Table?
Considered one of the most important chemistry reference tools, the periodic tableA chart organizing elements by atomic number and chemical properties into groups and periods. is a familiar sight around the world. The periodic table is an arrangement of the by their properties. An element is a substance in pure form, meaning that it cannot be broken down into any other substance. The smallest particle of an element is an atomThe smallest unit of an element, made up of protons and neutrons in its center, surrounded by moving electrons..
With one glance, the periodic table can provide a great deal of information on both individual elements and groups of them. A person familiar with the table can extract an element's relative mass, basic properties, and how it compares with its neighbors without knowing any facts about the element itself.
(The entire section is 4082 words.)