Periodic Table HistoryJohn Newlands arranged elements by increasing atomic mass where their properties repeasted every eight element-Mendeleev arranged the elements in order of increasing atomic mass with columns with similar properties (created first periodic table)-also predicted the existence and properties of undiscovered elements & left blank spaces in the table where he thought the undiscovered elements would go-Mosley arranged the elements in order of increasing atomic number rather than increasing atomic mass and the problems with the order of the elements in the periodic table were solved-periodic law is the periodic repetition of properties of elements when they are arranged by increasing atomic number-columns are groups and rows are called period-1A-8A are the representative elements-1A elements (except for hydrogen) are known as alkali metals-2A elements are known as the alkaline earth metals-1B-8B are the transition elements-B elements divided into transition metals and inner transition metals (located at bottom of PT)-7A are the halogens and 8A are the noble gasesClassification of ElementsEach of the group 1A elements has one electron in its highest energy level (thus each element has one valence electron)-atoms in the same group have similar chemical properties because they have the same number of valence electrons-the energy level of an elements valence electrons indicates the period on the periodic table in which it is found-gallium has a electron configuration of [Ar]4s23d104p1-valence electrons are in the fourth energy level and gallium is found in the fourth period-Because s orbitals hold a maximum of two electrons, the s-block portion of the periodic table (one all the way on the left) spans two groups-The p-block (one all the way on the right) three p orbitals can hold a maximum of six electrons spans six groups on the periodic table-the d-block (middle one) contains the transition metals five d orbitals...
Chemistry Study Notes - The Periodic Table and What Its Classification of Elements Tells Us
Essay by thekingandqueen, High School, 11th grade, March 2009
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