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Periodic Table - an arrangement of elements in order of...

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Periodic Table Even before we had this nice understanding of the atomic structure, scientists had  identified certain substances as  elements . So there were many attempts to arrange the  known elements so that there were some correlations between their known properties.  The first reasonably successful attempt was made by Dimitri Mendeleev  in 1869. He had  the idea of arranging elements in order of  increasing atomic mass  , and, most  importantly, found that elements with similar chemical and physical properties  occured periodically . He placed these similar elements under each other in columns. In 1914,  Henry Moseley  determined that a better arrangement was in order  of  increasing atomic number , giving us the  periodic table  we have today. We can define  the periodic table as 
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Unformatted text preview: an arrangement of elements in order of increasing atomic number placing those with similar chemical and physical properties in columns. Features of the Periodic Table Groups Vertical columns are called groups. Elements within a group have similar chemical and physical properties. Groups are designated at the top by the numbers 1-8 and by the letters A and B. (Note: group labeling is somewhat arbitrary, so watch out for other designations, particularly with A and B.) A group elements- Representative or main group elements B group elements- Transition elements In addition to the number-letter designation, some groups have their own name. 1A → alkali metals 2A → alkaline earths 7A → halogens 8A → noble gases or rare gases...
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