Chapter 5
                             Chemical Periodicity                                Classification of the Elements
                                                                               OBJECTIVES:
                                                                                 �Explain why you can infer the 
                                                                                   properties of an element based on 
                                                                                   those of other elements in the 
                                                                                   periodic table.
                                                                                 �Use electron configurations to 
                                                                                   classify elements as noble gases, 
                                                                                   representative elements, transition 
                                                                                   metals, or inner transition metals.
                   GHS Honors Chem                                             GHS Honors Chem
                        Periodic Table Revisited                                        Mendeleev’s Table
                   � Russian scientist Dmitri Mendeleev                        � Grouped elements in columns by similar 
                     taught chemistry in terms of                               properties in order of increasing atomic 
                     properties.                                                mass.
                   � Mid 1800’s - molar masses of                              � Found some inconsistencies - felt that 
                     elements were known.                                       the properties were more important than 
                                                                                the  mass, so switched order.
                   � Wrote down the elements in order of                       � Also found some gaps.
                     increasing mass.                                          � Must be undiscovered elements.
                   � Found a pattern of repeating                              � Predicted their properties before they 
                     properties.                                                were found. 
                   GHS Honors Chem                                             GHS Honors Chem
                   Mendeleev's Periodic Table                                     The Modern Periodic Table
                                (1871)                                         � Elements are still grouped by properties.
                                                                               � Similar properties are in the same 
                                                                                 column.
                                                                               � In 1913, Moseley changed the order to 
                                                                                 increasing atomic number.
                                                                               � This added a column of elements 
                                                                                 Mendeleev didn’t know about.
                                                                               � The noble gases weren’t found because 
                                                                                 they didn’t react with anything.
                   GHS Honors Chem                                             GHS Honors Chem
                                                                                                                                         1
                       � Horizontal rows are called Periods                              Vertical columns called groups
                       � There are 7 periods                                             Elements are placed in columns by 
                   1                                                                    similar properties
                   2                                                                     Also called families
                   3
                   4
                   5
                   6
                   7
                   GHS Honors Chem                                               GHS Honors Chem
                           The elements in the A groups are 
                           called the REPRESENTATIVE          8A
                     1A    elements                            0                         The group B are called the 
                       2A outer s or p filling    3A 4A 5A 6A7A                          transition elements
                                                                                                 These are called the inner 
                                                                                                 transition elements, and they 
                                                                                                 belong here
                   GHS Honors Chem                                               GHS Honors Chem
                     � Group 1A are the alkali metals                               � Group 7A is called the Halogens
                     � Group 2A are the alkaline earth metals                       � Group 8A are the Noble Gases
                   GHS Honors Chem                                               GHS Honors Chem
                                                                                                                                             2
                          Why is the Periodic Table arranged                                            H       1         Group 1A Alkali metals
                                    in Groups and Periods?                                                1 1s                         •   1 Valence Electron
                                                                                                        Li      2   1                      •  s1 configuration
                                                                                                          3 1s 2s
                        � The part of the atom another atom sees                                                2   2   6   1           •   Become +1 ions to
                           is the electron cloud.                                                       Na 1s 2s 2p 3s                  obtain the OCTET of
                           More importantly the outside orbitals.                                        11                                          electrons
                        �                                                                               K       2   2   6   2   6   1
                                                                                                         19 1s 2s 2p 3s 3p 4s
                        � The orbitals fill up in a regular pattern.
                                                                                                        Rb      2   2   6   2   6   2    10   6   1
                        � The outside orbital electron                                                   37 1s 2s 2p 3s 3p 4s 3d 4p 5s
                           configuration, or VALENCE electron                                           Cs      2   2   6   2   6   2    10   6   2    10    6   1
                           configuration, repeats.                                                       55 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d                5p 6s
                        � The properties of atoms repeat.                                               Fr      2   2   6   2   6   2    10   6   2    10   6   2
                                                                                                         87 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4
                                                                                                                14    10   6   1
                                                                                                               f   5d 6p 7s
                        GHS Honors Chem                                                                GHS Honors Chem
                          Group 2A Alkaline Earth Metals                                              Group 7A Halogens
                                   2   2             •   2 Valence Electrons                          •  7 Valence Electrons
                        4Be:  1s 2s                       •   s2 configuration                             2 5
                                                        •  Become +2 ions to                          •  s p configuration                             2  2   5  
                                    2   2    6   2                                                    •  Become -1 ions to achieve                  1s 2s 2p     9F
                        12Mg:  1s 2s 2p 3s                  obtain OCTET of
                                    2   2   6   2   6   2                                                their octet of electrons               2  2   6  2   5
                        20Ca:  1s 2s 2p 3s 3p 4s                     electrons                                                               1s 2s 2p 3s 3p 17Cl
                                                                                                                                    2  2   6  2   6  2  10   5  
                                   2   2   6   2    6   2   10    6  2                                                           1s 2s 2p 3s 3p 4s 3d 4p 35Br
                        38Sr:  1s 2s 2p 3s 3p 4s 3d 4p 5s
                                                                                                                        2   2  6   2  6   2  10   6  2  10   5    
                                    2   2   6   2   6   2    10   6   2   10                                          1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p          53I
                        56Ba:  1s 2s 2p 3s 3p 4s 3d 4p 5s 4d
                                                                                                         2  2   6  2  6   2  10   6  2   10  6  2   14  10   5  
                                         6   2                                                        1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 85At
                                      5p 6s
                                   2   2   6   2   6   2    10   6   2    10   6
                        88Ra: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p
                                         2  14    10   6   2
                                      6s 4f 5d 6p 7s
                        GHS Honors Chem                                                                GHS Honors Chem
                         Group 8A Noble Gases                                2He                           Can we determine an element 
                         •  8 Valence Electrons                            1s     2                    simply from the Valence Electron 
                              2 6
                         •  s p configuration                                  Ne
                                                                     2   2   6                                         Configuration?
                         •  Not reactive, have their              1s 2s 2p       10
                            octet of electrons
                                                             2   2   6   2   6 Ar
                                                          1s 2s 2p 3s 3p         18                                      Let’s try it …
                                               2   2   6   2    6   2   10   6 Kr
                                            1s 2s 2p 3s 3p 4s 3d 4p              36
                                                                                                                           1. 3s2        Mg
                                 2   2    6   2   6   2   10    6   2   10   6                                                   2    4
                              1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p Xe                                                          2. 5s 5p      Te
                                                                                 54                                              2    6
                                      2   2   6   2   6   2    10   6   2   10                                             3. 4s 3d Fe
                                   1s 2s 2p 3s 3p 4s 3d 4p 5s 4d Rn
                                                           6   2   14   10   6   86
                                                        5p 6s 4f 5d 6p
                        GHS Honors Chem                                                                GHS Honors Chem
                                                                                                                                                                                  3
                             Lewis Dot Structures                                                Lewis Dot Structures
                     � Lewis Dot structures are helpful in                                   K                    The number of unpaired 
                       visualizing bonding between atoms.                                                            dots corresponds to 
                                                                                             Ca                      the number of bonds 
                     � Dots correspond to the number of                                      In                        that the atom can 
                       valence electrons. These are the                                                               form in a compound. 
                       electrons that are involved in                                        C
                       interactions between atoms.                                           P                       What about ions?
                     � Dots are placed around the element’s                                                            2-
                       symbol, 1 at a time, until pairing is                                 S                       0
                       necessary.                                                                                    Br-
                                                                                             F
                     GHS Honors Chem                                                     GHS Honors Chem
                             Lewis Dot Structures
                     GHS Honors Chem
                                                                                                                                                           4