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notes3 - Unit 3 The Periodic Table Nomenclature and Bonding...

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Unit 3 – The Periodic Table, Nomenclature and Bonding Classification of Matter History of the Periodic Table Early Classification Dobereiner’s Triads: (1817) Groups of three elements with similar properties Cannizzaro’s method for determining atomic mass: (1860) Was adopted as the standard for determining atomic mass at the First International Congress of Chemists in Karlsruhe, Germany Newland’s Law of Octaves: (1863) When arranged by atomic mass, every 8 th element had similar properties Mendeleev’s Periodic Table: (1869) Arranged elements in a table by atomic mass. Elements with similar properties were grouped in columns. Mendeleev left empty spaces for elements that were “undiscovered”. He used his table to predict the properties of these elements (Sc, Ga, Ge) right! Why did some elements (Ar & K, Co & Ni, I & Te) not follow the atomic mass pattern? Why were the properties periodic? The Modern Periodic Table Moseley’s Atomic Number: (1911) led to the arrangement of the periodic table by increasing atomic number; retained columns with similar properties Modern Periodic Law: The properties of the elements are periodic functions of their atomic numbers Arrangement of the Modern Periodic Table Physical Property: a characteristic of a substance that can be observed or measured without changing the identity of the substance Chemical Property: a description of a substance’s ability to react (or not react). Changes into a new substance as a result of the observation or measurement. General Properties of the Elements Metals: left of the staircase and Al Good conductors of heat and electricity, malleable, ductile, shiny, high melting points, mostly solids (Hg is the exception), few valence e- Nonmetals: right of the staircase and H Poor conductors of heat and electricity, are gases or dull, brittle solids, low melting points, 5-7 valence e- Metalloids (semimetals): touching the staircase except Al Solids, have some properties of metals and nonmetals, semiconductors Families or Groups (columns) Main Group Elements (s & p blocks) Alkali Metals – Group I most reactive metals, not found free in nature, silvery, soft, react vigorously with H 2 O, lose e- in reactions, general valence structure ns 1 Alkaline Earth Metals – Group 2 reactive, not found free in nature, harder, denser, stronger than Group I, lose e- in reactions, general valence structure ns 2 Halogens – Group 17 most reactive nonmetals, “salt formers”, gases (F, Cl), liquid (Br), solids (I, At), gain e- in reactions, general valence structure ns 2 np 5 Noble Gases – Group 18 stable, unreactive elements (although some can form compounds), discovered between 1894-1900, general valence structure ns 2 np 6 , He is the exception Transition elements (d block) – metallic properties, less reactive, harder & stronger than s-block, sum of the outer “s” and “d” electrons gives the group number, variable oxidation numbers (charges), often form colored ions, deviation in e- configurations Inner Transition Elements or Rare Earth Elements (f block)
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