1. 2/20 p. 32 Periodic Table History IQ: On the PT, most elements are a. non-metals, on left hand side b. metals, on right hand side c. non-metals on right hand side d. metals on left hand side. Mendeleev crash course Mendeleev crash course (Acc)

2. Periodic – means regular, repeated pattern.

3. Video

4.  A way of organizing & classifying elements  Arranged in rows called periods and columns called groups or families.

5.  1860’s a Russian Scientist named Dmitri Mendeleev  discovered a system for organizing all of the known elements.  To help him find a pattern he put all of the known information on individual cards.  He listed the elements’ known properties.

6.  Patterns appeared when elements were arranged in order of increasing atomic mass.  However, this did not always produce similar groups. So he moved the cards into the group it best fit.  This left blank spaces on the table. Mendeleev Animation

8.  Mendeleev predicted that the blank spaces would be filled by elements that had not yet been discovered.  He even predicted the properties of new elements.  Published his table in 1869; the new elements were discovered within 16 years.

9.  Elements are now arranged by increasing atomic number  An element’s properties can be predicted from its location on the table.  Across a row or down a column the elements’ properties change in a predictable way.

10.  The table works because it is based on the structure of atoms, especially the valence e- s (outermost shell).  Atomic # increases by 1, so it has 1 more valence electron than the previous family.  Atomic # increasing by 1 means it has one more proton than the previous atom.

11.  List an element that is in the same Period as Phosphorus (P)