1. The Periodic Table I. History of the Periodic Table  Mendeleev  Moseley

2. Why is the Periodic Table important to me?  The periodic table is the most useful tool to a chemist.  It organizes lots of information about all the known elements.

3. Pre-Periodic Table Chemistry …  …was a mess!!!  No organization of elements.  Imagine going to a grocery store with no organization!!  Difficult to find information.  Chemistry didn’t make sense.

4. Periodic  Periodic Table  Something periodic occurs at regular or at least generally predictable intervals  Periodic Table of Elements – a table of the elements, arranged by atomic number, that shows the patterns in their properties; based on the periodic law

5. Periods  The horizontal rows of the periodic table.  Elements in a period are not alike in properties. n a period is always an inactive gas.

6. Groups  The vertical (up and down) columns of the periodic table (there are 18).  Elements in the same group or family have similar characteristics or properties.

8. Dmitri Mendeleev  Dmitri Mendeleev (1869, Russian) Organized elements by increasing atomic mass. Predicted the existence of undiscovered elements. Elements are periodic meaning that they have a regular or repeating pattern

10. Mendeleev’s Predictions  Although Mendeleev’s Periodic Table of Elements had missing elements or “gaps,” he was able to predict the characteristics of these missing elements because of Periodic Law. Date Predicted 1871Date Discovered 1886 Atomic Mass72Atomic Mass72.6 Density5.5 g/cm 3 Density5.47 g/cm 3 Bonding Power 4 4 ColorDark GrayColorGrayish White “Ekasilicon”Germanium Notice how Mendeleev’s predictions (orange column) were very accurate when compared to Germanium’s actual characteristics (green column)

11. Henry Moseley  Henry Moseley (1913, British) Organized elements by increasing atomic number. Based on periodic law which states that chemical and physical properties of elements are based on their atomic number.

13.  Metals  Nonmetals  Metalloids

14. Properties of Metals  Found on the left side of the periodic table  Good conductors- able to transfer heat and electricity  Malleable- able to be flattened and shaped without breaking  Ductile- able to be drawn into long thin wires  Luster- able to reflect light (shiny)

15. Properties of Nonmetals  Found on the right side of the periodic table  Not malleable or ductile but are often brittle  Not shiny  Poor conductors of heat and electricity

16. Properties of Metalloids  Separate the metals from the nonmetals  Have some properties of metals and nonmetals.  Example, most metalloids conduct electricity better than nonmetals but not as good as metals.