 Write the short hand configurations for the following elements: ◦ Molybdenum, Selenium, Strontium, Ruthenium, and Antimony  Write the number of valence electrons the previous elements have  Based on its group, how many valence electrons will Bromine have? Prove this.  Draw the electron dot diagram for Oxygen and Silicon

The Periodic Table Pg.45

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 Only knew 23 elements in 1790  Discovery of electricity brought change  Dmitri Mendeleev demonstrated a connection between atomic mass and elemental properties (1869)  Saw a repeating pattern  Left blank spaces where undiscovered elements should go (Sc, Ge, and Ga)  Henry Moseley rearranged the table according to atomic number  A clear repetition of repeating physical and chemical patterns emerged. Called periodic law

 The columns on the periodic table are called groups (or families) ◦ Elements in the same group have similar chemical and physical properties  The rows are called periods  Main group elements (representative elements): Groups 1-2,  Transition elements: Groups 3-12  Sometimes see a number/letter system  Can find elements based on group and period

 There are 3 major groups on the periodic table: ◦ Metals ◦ Nonmetals ◦ Metalloids (or semiconductors)

 The metals are on the left side of the periodic table  Malleable and ductile  Shiny  Good conductors of heat and electricity  They further broken into 4 categories ◦ Alkali metals ◦ Alkaline Earth metals ◦ Transition elements ◦ Inner transition elements

 Are on the right side of the stair-step (except H)  Can be gases  Brittle and dull  Poor conductors of heat and electricity  Br only nonmetal that is a liquid at room temp  Can be broken into smaller categories ◦ Halogens ◦ Noble gases ◦ Carbon group

 Border the stair step line  Have properties of both metals and nonmetals  Si and Ge most important as they are used in computer chips