The Periodic Table of Elements

Early Versions 1830: 55 elements had been discovered 1860’s: Dimitri Mendeleev discovered a system that applied to all elements

Mendeleev Father of the periodic table Noticed patterns when the elements were arranged by increasing atomic mass

Mendeleev Noted properties of elements Melting point Density Color Studied atomic mass and chemical bonds Compared mass to hydrogen

Mendeleev Noted that arranging elements according to atomic mass did not always produce similar groups Moved element cards into groups where they fit best Predicted other elements and their properties

Mendeleev 1869: Published the 1st periodic table

The Modern Periodic Table New elements were added as they were discovered Early 1900’s: scientists learned about the atomic number

Reading the Periodic Table Contains over 100 squares: one for each element

Reading the Periodic Table An element’s properties can be predicted from its location on the periodic table. groups/families periods

Groups/Families Elements in columns 18 columns Elements in each group have similar characteristics. Example: Group 1 are metals that all react violently with water; Group 17 reacts violently with elements from Group 1; Group 18 rarely reacts at all

Groups/Families EXAMPLES OF FAMILIES - Alkali Metals - Alkaline Earth Metals - Transition Metals - Halogen Gases - Inert Gases (Noble Gases)

Periods Horizontal rows Series of different elements from different groups Have very different properties

Why it Works! It’s based on the structure of atoms, especially the valence electrons!