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3.1 Periodic Table (Ashley Vokral)
Added by Mary Blackwell, last edited by Mary Blackwell on Oct 18, 2007
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Group 2: Many Electron Atoms, Periodic Table of the Elements, and Periodic Properties II. Periodic Table

A.   History

-  The periodic table was originally constructed to represent the patterns observed in the chemical properties of the elements.

-  Chemists who attempted to explain patterns:

            1. Johann Dobereiner- triads (i.e. chlorine, bromine, iodine)

            2. John Newlands- octaves, idea that certain properties seemed to repeat for every eighth element

            3. Dimitri Ivanovich Mendeleev- developed the current periodic table

                -  Grouped the elements on the basis of similarities in their chemical properties

                -  Left blank spaces at appropriate places where additional elements would occur

                - Questioned values of atomic weights when they disagreed with the pattern of elements (changed beryllium, indium, and uranium)

                -  The periodic table can correctly predict the existence and properties of still unknown elements.



A common and popular version of the periodic table (from http://www.chem.wisc.edu/areas/reich/handouts/periodic-table.GIF).
-  Each group contains compounds with similar electron configurations; except hydrogen and helium.

- The periodic table is organized by atomic number, reading left to right-top to bottom.

- Groups are the columns across the top numbering 1-18 with elements of the same valance electron in the column

-  Periods are the rows on the side numbering 1-7 with a row having a common set of quantum numbers.

-  The periodic table is organized containing many trends which will later be explained.

-  In the periodic table elements are grouped into eight classes according to their properties.

                  a. Metals

                       - Largest group of elements.

                       - Characterized with physical properties such as efficient conduction of heat and electricity, malleability, ductility, and a lustrous appearance.

                      - Tend to lose electrons to form positive ions.

                                1. Alkali Metals- group 1A

                                   Are very active elements that readily form ions with a 1+ charge when they react with nonmetals.

                                2. Alkaline Earth Metals- group 2A

                                   Form ions with a 2+ charge when they react with nonmetals.

                               3. Transition Metals- group 3B-2B

                               4. Lanthanide Series- usually subset below table

                               5. Actinide Series- usually subset below table underneath Lanthanide series

                               6. Other Metals.

          b. Nonmetals

              - Smaller group of elements

              - Resides in the upper right hand corner of the periodic table

              - Nonmetals tend to gain electrons in reactions with metals to form negative ions

                         7. Halogens- group 7A

                            Form diatomic molecules and react with metals to form salts containing ions with a 1- charge.

                        8. Noble Gases- group 8A

                           Exist under normal conditions as monatomic (single atom) gases and have little chemical reactivity.

B.    The Elemental Square

-  The typical elemental square contains the element name, atomic weight, atomic symbol and the atomic number (Z).

          a. Element- A substance that cannot be decomposed into a simpler substance by a chemical reaction. A substance composed of only one kind of atom.

          b. Atomic Weight- The weighted average of the atomic masses of the different isotopes of an element. Sometimes known as the atomic mass units (amu).

         c. Atomic Number (Z)- The number of protons in the nucleus of an atom.

         d. Atomic Symbol- Abbreviations to the current element name or the exception of the original name in Latin (i.e. Ag, Fe, K, Au and Pb).


Elemental square for Carbon (from www.cartage.org.lb.../Elements.htm*)*
-  Also visible on some periodic tables is the radioactive symbol. This occurs with all elements after element 83.



Radioactive symbol (from www.acsu.buffalo.edu/~btboeing/*).

Word document form of wiki: *Group 2 Ashley Vokral-periodic table.doc

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