1. Section 2 – pg 131 Organizing the Elements
Chapter 4
Section 2 – pg 131
Organizing the Elements

2. Mendeleev’s Periodic Table
Pg 132
Mendeleev’s Periodic Table
By 1869 a total of 63 elements had been discovered
A Russian scientist, Dmitri Mendeleev, discovered a set of patterns that applied to all the elements

3. Patterns of Properties
Pg 132
Patterns of Properties
To find the pattern of the elements Mendeleev wrote each element’s melting point, density, color and atomic mass on individual cards
Atomic Mass: the average mass of all the isotopes of an element
Mendeleev tried arranging the cards in many ways
Mendeleev noticed that a pattern of properties appeared when he arranged the elements in order of increasing atomic mass

4. Mendeleev published the first periodic table
Pg 132
After putting the elements in order by atomic mass, he grouped them together based on other characteristics
Mendeleev published the first periodic table
A periodic table is an arrangement of elements showing the repeating pattern of their properties

5. Predicting New Elements
Pg 133
Predicting New Elements
When arranging the elements by atomic mass, sometimes the elements did not always group similar elements together
Mendeleev moved these elements to be in groups of similar properties, leaving three blank spots
Mendeleev predicted that these spots would be filled with elements not yet discovered but would have the properties of the groups they fit into
Within 16 years, scientists discovered three missing elements that had properties similar to what Mendeleev predicted (scandium, gallium, germanium)

6. Gallium
(69.72)
Germanium
(72.59)
Scandium
(44.956)

7. The Modern Periodic Table
Pg 133
The Modern Periodic Table
The elements are arranged in order of increasing atomic number (the number of protons)
Mendeleev’s arranged by atomic mass
The properties of an element can be predicted from its location on the periodic table

9. Pg 136
Classes of Elements
Metals
Semimetals
Nonmetals
Inert Gases

10. Periods Horizontal rows of the periodic table
Each row increases in mass: left to right
Total of 7 periods

11. Groups Pg 136 The vertical columns of the periodic table AKA: family
Consists of elements with similar characteristics
Group 1: react violently with water
Group 2 reacts with water slowly or not at all
Group 17: react violently with Group 1 elements
Group 18: rarely react at all

12. Reading the Data Pg 137 Atomic Number (# of protons) Chemical Symbol
A representation of an element usually consisting of two letters
Element Name
Atomic Mass
(average mass of all the isotopes)

13. Chapter 4 Section 2 Homework – pg 137

14. 1A. In what order did Mendeleev arrange the elements in his periodic table?

15. 1B. What pattern did Mendeleev discover when he arranged the elements?

16. 1C. What elements did Mendeleev group with lithium in his periodic table?

17. 2A. What information is listed in an elements square in the periodic table?

18. 2B. Describe two differences between Mendeleev’s periodic table and the modern periodic table.

19. 2C. What element has 47 protons in its nucleus?