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History of the Periodic Table: Difference between revisions
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== Mendeleev's Periodic Table == | == Mendeleev's Periodic Table == | ||
Almost all of the credit for the periodic table goes to Dmitri Mendeleev. He arranged the elements by their atomic mass, like Newlands, but he did something different. He added in the elements that had not been discovered yet. He decided to do this because while he was studying the atomic masses he noticed that when they were put in order some of them increased more than others. | Almost all of the credit for the periodic table goes to Dmitri Mendeleev. He arranged the elements by their atomic mass, like Newlands, but he did something different. He added in the elements that had not been discovered yet. He decided to do this because while he was studying the atomic masses he noticed that when they were put in order some of them increased more than others. <ref name=BJU> He also arranged them vertically (http://www.bbc.co.uk/schools/gcsebitesize/science/add_edexcel/atomic_structure/periodictablerev1.shtml), and added the transition metals. He recognized that the transition metals did not fit into the chart so he separated them from the rest of the periodic table. Mendeleev summarized his work by writing the periodic law. The law states, "The properties of elements vary with their atomic masses in a periodic way". (BJU Chemistry, Third Edition) | ||
== The Modern Periodic Table == | == The Modern Periodic Table == | ||
Although Mendeleev's periodic table was brilliant, there were still some things wrong about it. The way that the elements were arranged still did not always group the elements that were similar. One of Ernst Rutherford's assistants, Henry Moseley, suggested that they develop a way to count the number of protons in an atom's nucleus. Once he created a way to do this, he realized they needed to revise the periodic table to make it more accurate, now that they could find the number of protons in an atom. He changed the periodic table and the periodic law. The modern periodic law states, "The properties of elements vary with their atomic numbers in a periodic way". | Although Mendeleev's periodic table was brilliant, there were still some things wrong about it. The way that the elements were arranged still did not always group the elements that were similar. One of Ernst Rutherford's assistants, Henry Moseley, suggested that they develop a way to count the number of protons in an atom's nucleus. Once he created a way to do this, he realized they needed to revise the periodic table to make it more accurate, now that they could find the number of protons in an atom. He changed the periodic table and the periodic law. The modern periodic law states, "The properties of elements vary with their atomic numbers in a periodic way". <ref name=BJU> | ||
The modern periodic table has more than the 63 elements that were discovered by Mendeleev. Most of the periodic tables up to this date have up to 109 elements. It has 18 groups in vertical columns. The vertical columns are labeled by roman numerals or numbers, and each horizontal row is called a period, and the periodic table consists of seven periods. https://genesismission.jpl.nasa.gov/educate/scimodule/cosmic/explore_2ST.pdf | The modern periodic table has more than the 63 elements that were discovered by Mendeleev. Most of the periodic tables up to this date have up to 109 elements. It has 18 groups in vertical columns. The vertical columns are labeled by roman numerals or numbers, and each horizontal row is called a period, and the periodic table consists of seven periods. https://genesismission.jpl.nasa.gov/educate/scimodule/cosmic/explore_2ST.pdf | ||
