Student Resources

Figure 2.14 The Periodic Table Corresponds to the Filling Patterns of the Electron Shells and Subshells.
This organization on the periodic table makes it easy to predict where an atom’s electron configuration ends and explains why elements within a family share so many similar characteristics! This is because they all share the same outer shell or valence shell electron configuration.

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  Group 1A elements are the alkali metals and all have one electron in the outermost energy level because their electron configuration ends in s1.
  
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  Group 2A elements are the alkaline earth metals and all have two electrons in the outermost energy level because their electron configuration ends in s2.
  
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  All of the Transition Metals have two electrons in their outermost energy level because their highest shell electron configuration ends in s2.
  
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  Group 3A elements have three electrons in the outermost energy level because their electron configuration ends in s2p1.
  
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  Group 4A elements have four electrons in the outermost energy level because their electron configuration ends in s2p2.
  
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  Group 5A elements all have five electrons in the outermost energy level because their electron configuration ends in s2p3.
  
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  Group 6A elements all have six electrons in the outermost energy level because their electron configuration ends in s2p4.
  
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  Group 7A elements are the halogens and all have seven electrons in the outermost energy level because their electron configuration ends in s2p5.
  
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  Group 8A elements are the noble gases and all have eight electrons in the outermost energy level because their electron configuration ends in s2p6.
  
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  Elements in group 8A have the most stable electron configuration in the outermost shell because the sub levels are completely filled with electrons.
  

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Let’s do some practice problems using the following periodic table: