Subject: Why are there inconsistancies in electron configuration patterns?

In the periodic table, showing electon configurations, the transitional elements 
and rare earths, show an inconsistant increase in the number of electrons in the 
orbitals.  For example, AU-Gold has an electron configuration of  2-8-18-32-18-1 
instead of 2-8-18-32-17-2.  The 79th electron falls to the preceding transitional 
shell instead of remaining in the outter most represntative 6s orbital.  HG-
Mercury for example has both of its 6s electrons.  There are several other 
elements.  Some that give up two of their electrons to a preceding shell before 
eventually coming back to a "counting up" pattern.  What causes these "certain 
elements" to temporarily jump out of step, in the increasing progression of the 
tables electron configurations?  

Re: Why are there inconsistancies in electron configuration patterns?