Periodic Table Notes February 3rd

Dmitri Mendeleev: Father of the Table HOW HIS WORKED…  Put elements in rows by increasing atomic weight.  Put elements in columns by the way they reacted. SOME PROBLEMS…  He left blank spaces for what he said were undiscovered elements. (Turned out he was right!)  He broke the pattern of increasing atomic weight to keep similar reacting elements together.

The Current Periodic Table  Mendeleev wasn’t too far off.  Now the elements are put in rows by increasing ATOMIC NUMBER!!  The horizontal rows are called Periods and are labeled from 1 to 7.  The vertical columns are called Groups are labeled from 1 to 18.

Groups…Here’s Where the Periodic Table Gets Useful!!  Elements in the same group have similar chemical and physical properties!!  (Mendeleev did that on purpose.) Why?? They have the same number of valence electrons. They will form the same kinds of ions.

Group 1-Alkali Metals  Silvery Solids  Tarnish Rapidly  Low Densities  Low Melting Points  Very Soft Metals  Most Reactive Metals  React Strongly w/Halogens & Water (Violently)  1 Valance e -

Group 2-Alkaline Earth Metals  Silver in Color  Denser, Harder, and Higher Melting Points then Group 1  Very Reactive, but not as reactive as Group 1  React w/Halogens & Water  2 Valance e -

Group 17-Halogens  Toxic  Non Metals except for (At)  Salt Formers (specially w/Alkali & Alkaline Earth Metals)  Highly Reactive  7 Valance e -  Poor Conductors  Low Melting & Boiling Points  Only Group that contains all 3 States of room Temperature

Group 18-Noble Gases  All Gases  Known also as Inert Gases  Do NOT React w/Anything  8 Valance e -  Low Boiling Points  Odorless & Colorless

Metalloids  Between the Metals & Non Metals  Share Properties w/both Metals and Non Metals  Makes Good Semi- Conductors  Used in Computer Industry

Transition Metals  Group 3 to Metalloids  Higher Melting Points  Used in a Variety of Products

Non Metals  Include everything from the right hand side of the Metalloids including Hydrogen  Usually Gases or Brittle Solids  Poor Conductors  Good Insulators & Semi Conductors  Little or no Luster

Lanthanides  Atomic #’s  Known as the Rare Earth Metals  Used in lamps, lasers, magnets, motion picture projectors, & X- ray intensifying screens  Used as catalysts in the production of petroleum & synthetic products

Actinides  Atomic #’s  Radioactive  Unstable and decay to form other elements  Most are synthetic except for (Th), (Pa), & (U)  Very Dense  React w/boiling water or dilute acid to release hydrogen gas