 Created modern periodic table (late 1800’s)  Arranged by increasing atomic number  Similar elements found in columns

 Elements are in columns called groups or families  All elements within a group have similar chemical properties  Horizontal rows are called periods

 Representative elements are chemically active elements  Transitional metals are in center of the table  Inner transitional metals are the two rows below

 s, p, d, and f

 Every group on the table ends in the same basic configuration, this gives them their characteristic properties ◦ Group 1 s 1 ◦ Group 2 s 2 ◦ Group 3 s 2 d 1 ◦ Group 12 s 2 d 10 ◦ Group 13 s 2 d 10 p 1

 Period of the element tells the highest main level reached  What is end configuration of each ◦ Ca ◦ Si ◦ Ga