Unit 1 B.1, B.2

In the 1800s, scientists had discovered about 60 elements.  They were trying to figure out the bet way in which to organize them by placing the elements with similar properties near each other on a chart.  A Russian chemist named Dimitri Mendeleev published a periodic table with a layout similar to a monthly calendar.  In the 1800s, two characteristics determined the organization of periodic tables: the element's average atomic mass (which is a physical property) and it's "combining capacity" (which is a chemical property).  In the early periodic tables, elements that had similar chemical properties were put into columns together, while increasing atomic masses decided the rows.  Therefore, the elements on the left hand side of the table were very reactive while the elements on the right were not.