Organizing the Elements

Dmitri Mendeleev Russian 1869 Looking for patterns in element behaviors

Patterns F and Cl both irritating gasses Cu and Ag both tarnish when exposed to air Li, Na, K react violently with water

Atomic Mass Patterns appeared when arranged in order of increasing Atomic Mass Atomic Mass: Avg. mass of all the isotopes of that element

Predicting When arranged not all elements agreed with the patterns Mendeleev predicted that more elements existed (SC, Ga, Ge) and their properties Within 16 years they were found

Today’s Table Properties of elements repeat in periods ◦ Periods are the rows 1913 Henry Moseley measures charges

Moseley Rearranges by atomic number ◦ Elements can now be identified by their protons as opposed to their Atomic Mass

Symbol Most are English abbreviations Find some elements and their symbols that are not Look on pg 85

Organization Properties of elements can be predicted from its location on the table Periods Groups

Periods Rows Moving across the properties of elements change to pattern Left = highly reactive metals Right = unreactive gasses 7 periods

Groups Columns Also called families Elements in each group have similar properties 18 groups

Al Look at the different items List as many properties as you can about each Why is Al used to make each item? What other items are made from Al? What other elements have similar properties?

Assignment Pg all parts Exit Slip: write 3 things you learned about the Periodic Table of Elements