1A                   group # = # valence (outside) e-                    8A
              1       2A                                             3A 4A 5A 6A 7A
              2
        Row 3             3B 4B 5B 6B 7B 8B 8B 8B 1B 2B
         =    4
      # shells 5   s                        d                                 p
              6
              7
                               6
                               7                              f
                   Electron Configuration
                                         1
                                   1s
                       row #                           group #
                       shell #                       # valence e-
                possibilities are 1-7              possibilities are:
                       7 rows                          s: 1 or 2
                                    subshell            p: 1-6
                                possibilities are       d: 1-10
                                  s, p, d, or f         f: 1-14
                                  4 subshells Total e- should equal
                                                       Atomic #
                                                                   1
              What element has an electron configuration of 1s ?
                           Practice:
          Ask these questions every time you have to write an 
                        electron configuration
       •   Lithium:
          1.  find the element on the periodic table atomic # = 3
          2.  what is the period number? 2
          3.  how many shells? 2
          4.  what is the group number? 1
          5.  how many valence electrons? 1
                                          s
          6.  what subshell(s) does Li have? 
                                               2  1
          7.  what is the electron configuration? 1s 2s
                           Practice:
          Ask these questions every time you have to write an 
                        electron configuration
       •   Boron:
          1.  find the element on the periodic table atomic # = 5
          2.  what is the row #? 2
          3.  how many shells? 2
          4.  what is the group #? 3
          5.  how many valence electrons? 3
          6.  what subshell(s) does B have? p
                                               2  2   1
          7.  what is the electron configuration? 1s 2s 2p