Warm Up Describe how the periodic table is arranged.

The Periodic Table: Organizing the Elements Chapter 6

Dobereiner’s Triad (1829) Organized the elements into groups of three (triads) according to similar properties. Example: Halogen Triad – Chlorine, Bromine, & Iodine React easily with metals. Atomic mass of bromine is approximately halfway between the atomic masses of chlorine and iodine. PROBLEM: Not all known elements could be grouped into triads. (Iron, Manganese, Nickel, Cobalt, etc.)

Mendeleev’s Periodic Table (1869) Dmitri Mendeleev, Russian chemist Organized ~60 elements by INCREASING ATOMIC MASS. Elements arranged in groups according to repeating properties. Predicted properties of undiscovered elements. Mendeleev is credited with the creation of the Periodic Table.

Mendeleev’s Periodicity of Elements

Mendeleev’s First Periodic Table of Elements

Mendeleev’s Periodic Table of Elements

Moseley’s Periodic Table (1913) The Modern Periodic Table Organized by INCREASING ATOMIC NUMBER. Differences from Mendeleev: Argon & Potassium Cobalt & Nickel Tellurium & Iodine Elements in vertical columns have similar properties. PERIODIC LAW: Physical and chemical properties of elements repeat in a regular pattern when they are arranged in order of increasing atomic number.

Understanding the Periodic Table Vertical Columns: Groups or Families Horizontal Rows: Periods Divided into three main categories: Metals: Left Side Nonmetals: Right Side Metalloids (Semi-Metals): Along Zig-Zag Line

Metals Left of zig-zag line Properties: Excellent conductors of heat and electricity High luster (shiny) All are solids at room temperature (except Mercury) Many are malleable & ductile. Malleable: can be hammered into a sheet Ductile: can be drawn into a wire Valence electrons: Most have 1, 2, or 3 Held loosely (LOSE electrons to form compounds).

Metals Transition & Inner Transition elements are metals Inner Transition Elements located below the table Lanthanides – Rare Earth Elements Actinides – All are Radioactive & those beyond Uranium are not found in nature.

Nonmetals Right of zig-zag line Properties: Many are gases at room temperature. Those that are solid at room temp. lack luster. Carbon & Phosphorus - solids Bromine & Iodine – liquids Poor conductors of heat and electric current. Brittle Valence electrons: Most have 5, 6, 7, or 8 Held tightly (GAIN or SHARE electrons to form compounds).

Metalloids (Semi-metals) Along the zig-zag line (except Aluminum) Properties of both metals & nonmetals. Some are Semiconductors: silicon, germanium, arsenic Silicon is generally a poor conductor of electricity. If a small amount of Boron is mixed in the silicon (doping), the mixture is a good conductor. (Used to make computer chips).

Metals – Green Nonmetals – Orange Metalloids - Purple

Classifying the Elements Periodic Table Groups Group 1 (1A) Alkali Metals Most reactive metal group Most reactive element: Francium Never found uncombined in nature 1 valence electron Loses 1 electron to form compounds Oxidation number: 1+

Classifying the Elements Periodic Table Groups Group 2 (IIA) Alkaline Earth Metals Very reactive metals 2 valence electrons Loses 2 electrons to form compounds Oxidation number: 2+

Classifying the Elements Periodic Table Groups Group 3-12 (B groups) Transition Elements & Inner Transition Elements Variable number of valence electrons & oxidation numbers

Classifying the Elements Periodic Table Groups Group 13 (IIIA) Boron Family 3 valence electrons Shares 3 electrons to form compounds Oxidation number: 3+

Classifying the Elements Periodic Table Groups Group 14 (IVA) Carbon Family 4 valence electrons Shares 4 electrons to form compounds Oxidation number: 4±

Classifying the Elements Periodic Table Groups Group 15 (VA) Nitrogen Family 5 valence electrons Gains 3 electrons to form compounds Oxidation number: 3-

Classifying the Elements Periodic Table Groups Group 16 (V1A) Oxygen Family 6 valence electrons Gains 2 electrons to form compounds Oxidation number: 2-

Classifying the Elements Periodic Table Groups Group 17 (VIIA) Halogens Form salts when combined with alkali metals Most reactive nonmetal group Most reactive: Fluorine 7 valence electrons Gains 1 electron to form compounds Oxidation number: 1-

Classifying the Elements Periodic Table Groups Group 18 (VIIIA) Nobel Gases Nonreactive (Inert) Gases Rarely react in chemical reactions s & p sublevels of outer energy level is completely filled 8 valence electrons Exception: Helium – 2 valence electrons Oxidation number: 0