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Pre-class Activity 12/18 How are library books classified? Why is such a classification system valuable? History of the Periodic Table John Newlands (1864) Recognized that when atoms are arranged by increasing mass, their properties repeated every eighth element which he named the “law of octaves” Elements with similar properties were arranged in the same row Did not work for all known elements Dimitri Mendeleev (1869) Organized the first periodic table Arranged elements by increasing atomic mass Was able to predict the existence and properties of yet undiscovered elements Modern Day Periodic Table Henry Moseley o Arranged elements according to increasing atomic number instead of increasing atomic mass o Demonstrated a periodic repetition of chemical and physical properties called the periodic law Pre-class Activity 1/5 What is the location, by group and period, of Boron? Group 13 Period 2 Which element is found in group 9, period 5? Rhodium Organization of the Periodic Table Group Period Main Group or Representative Group Elements p-block s-block Transition Elements d-block f-block Metals, Metalloids, and Nonmetals Metalloids Metals Transition Metals Inner Transition Metals Properties of Metals Shiny Smooth Solid at room temp Malleable Ductible Conduct Electricity Metalloids (Semimetals) Metalloids contain physical and chemical properties of both metals and non-metals 13 14 15 16 17 B C N O F Boron Carbon Nitrogen Oxygen Fluorine Al Si P S Cl Aluminium Silicon Phosphorus Sulfur Chlorine Ga Ge As Se Br Gallium Germanium Arsenic Selenium Bromine In Sn Sb Te I Indium Tin Antimony Tellurium Iodine Tl Pb Bi Po At Thallium Lead Bismuth Polonium Astatine Nonmetals Nonmetals are generally gases or brittle, dull-looking solids. They are poor conductors of electricity. classification of Elements s block p block 1 d block 2 3 4 5 3 4 6 5 7 6 4 5 f block Pre-class Questions 1/7 How many valence electrons does Antimony (Sb) have? What is it’s Lewis Dot structure? 5 Sb Which element is represented by the following electron configuration? [Xe] 6s24f143d8 Platinum (Pt) Periodic Trends in Atomic Radii Decreases Increases From one group to the next, atomic radius decreases because the the electrostatic attraction between increasingly larger nuclei increases, pulling the electrons closer to the nucleus From one row to the next, atomic radius increases because increasing numbers of neutrons shield the electrostatic force and valence electrons are located further and further away from the nucleus Periodic Trends in Ionic Radii Increases Increases Decreases For positive ions, charge numbers increase as more electrons are lost from the atom. The electrostatic force is greater for smaller numbers of electrons which decreases the ionic radius. For negative ions, as the charge number increases, so does the number of electrons. Electrostatic forces decrease and the ionic radius increases in size. From one row to the next, atomic radius increases because increasing numbers of neutrons shield the electrostatic force and valence electrons are located further and further away from the nucleus Periodic Trends in Ionization Energy The amount of energy required to remove an electron from an atom Increase Decrease Increased nuclear charge that occurs from one group to the next accounts for electrons being held more tightly within the atom. The more tightly they are held, the greater the amount of energy that is required to remove and electron from an atom. From one row to the next, ionization energy increases because increasing numbers of neutrons shield the electrostatic force and valence electrons are located further and further away from the nucleus Periodic Trends in Electronegativity Ability of an atom to attract electrons Increase Decrease