1. 14 The Periodic Table of Elements
Key Terms:
Substance: a particular kind of matter with uniform properties.
Element: a substance that cannot be broken down any further

2. In the late 1800s, Russian chemist Dmitri Mendeleev began to think about how he could organize the elements based on their properties.
He found that there were certain repeating patterns in the elements and he organized them into the Periodic Table of Elements

3. Organization of the Periodic Table:
Elements are arranged according to their atomic mass. Mass increases as you move from left to right.
Elements are also arranged according to their atomic number, or the number of protons in the atoms of different elements.

4. Elements on the table are arranged into columns and rows based on similar chemical and physical properties.
ROWS= (across) are called PERIODS
COLUMNS= (up and down) are called FAMILIES or GROUPS
Elements in a family/group have very similar chemical and physical characteristics and react in similar ways