1. Chapter 5: The Periodic Table Video

2. Section 1: Organizing the Elements Video 2

3. Recognizing a Pattern Dmitri Mendeleev: – In this periodic table, Mendeleev arranged elements in rows by increasing atomic mass – He was able to predict new elements – Few elements did not fit the pattern

4. Changing the Arrangement The modern periodic table organizes elements by atomic number. When the elements are arranged in this way, elements that have similar properties appear at regular intervals. Elements become less metallic across each period (each row of the table is a period) Elements in a group have similar properties (each column of the periodic table is a group)