1. Organizing the Elements
Chapter 4, Section 2
Organizing the Elements

2. Mendeleev He discovered a set of patterns that applied to all elements
He wrote properties of elements on individual cards
He then arranged them according to increasing atomic mass (average mass of all of an element’s isotopes)

3. Periodic Table
Group by group, Mendeleev arranged the 63 known elements based on their properties:
Melting point
If they tarnish
If they react with water
Etc.
Periodic means “in a regular, repeated pattern”
Table Talk: Discuss why Mendeleev put question marks in his original periodic table. (Hint, there were only 63 known elements at the time)
See Discovery Education video“Periodic Table” (3:55) – from “Greatest Discoveries with Bill Nye – Chemistry”

4. Modern Periodic Table More than 100 elements
Arranged in order of increasing atomic number (# of protons)
The properties of an element can be predicted from its location on the periodic table
See Active Art: enter code cgp-1032

5. Click here to see an interactive, illustrated version of the Periodic Table

6. More About the Periodic Table
Classes of Elements
Atomic numbers increase from left to right
Table is color-coded to classify types of elements
Metals
Non-metals
Inert gases

7. Periods Horizontal rows
The properties of the elements change from left to right in a pattern
Metals on left, with most reactive metals on far left
Non-metals on the right with most reactive next to the inert gases on the far right
Semi-metals between the metals and non-metals
Atomic mass increases from left to right
And from top to bottom

8. Groups Vertical columns Also known as a “family”
Consists of elements with similar characteristics
Lanthanides and actinides do not belong in the 18 groups and have been pulled out

9. Table Talk: Discuss the difference between groups and periods on the periodic Table

10. Reading the Data Calcium
In our textbook, each square on the Periodic Table lists 4 pieces of information:
An element’s atomic number
Chemical symbol
Name
Atomic mass
Calcium
Table Talk: Discuss what information the atomic number and atomic mass give us.
See BrainPop “Periodic Table” end