Daily Science Write the short hand configurations for the following elements: Molybdenum and Ruthenium Write the number of valence electrons Cobalt 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.41

History http://www.youtube.com/watch?v=0RRVV4Di omg

Discovery 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 physical and chemical patterns emerged. Called periodic law

The Modern Periodic Table 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, 13-18 Transition elements: Groups 3-12 Sometimes see a number/letter system Can find elements based on group and period

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

Metal 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

Nonmetals 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

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