Is the half-full rule and full rule followed in the 6th and 7th periods?
Short answer: no! The first known exception to occur in the periodic table is in period 5:  niobium’s ground state electronic configuration is


  $\ce{Nb: [Kr] 5s^1 4d^4}$


which is not warranted by the “usual” rules for determining electronic configuration. So, the “half-full rule” is not sufficient in periods 5 and higher.



Let’s look at Wikipedia’s list of exceptions to Madelung’s rule. In period 4, the only exceptions are $\ce{Cr}$ and $\ce{Cu}$, which are accounted for by the “half-full rule”. (Don’t bother too much about the dispute for Ni.)

In period 5, the exceptions to Madelung’s rule are classified in three groups:


$\ce{Mo}$ and $\ce{Ag}$: they are the analogues of Cu and Cr
$\ce{Pd}$ is $\ce{5s^0 4d^10}$: a different type of application of the explanation that “fully filled shells are particularly stable”, because in this case two electrons from the s shell were pulled into the d shell. Not what you usually learn.
$\ce{Nb}$ is $\ce{5s^1 4d^4}$,  and $\ce{Ru}$ is $\ce{5s^1 4d^7}$: these cannot be explained by simple rules, and one has to perform complex quantum chemistry calculations to understand these electronic configurations.


Period 6 contains further inconsistencies, because of the introduction of $\ce{f}$ orbitals into the mix.