In an electron configuration valence electrons 
are all electrons in the outermost shell and in 
any partially filled d or f subshells.
Core electrons are all electrons in inner energy 
levels including completely filled d and f 
subshells.
For germanium, n=4 is the highest shell so the 
two electrons in the 4s and two electrons in the 
4p subshells are all valence electrons.
Since the 3d subshell is fully filled, those 
electrons are considered core electrons along 
with the remaining 18 electrons
 in the 1s, 2s, 2p, 3s, and 3p subshells.
Let's determine how many core and valence 
electrons lead has.
Based on the periodic table, lead's electron 
configuration is xenon, 6s2 4f14 5d10 6p2.
n=6 is the highest energy level, so the two 
electrons in the 6s subshell 
and the two electrons in the 6p subshell are 
valance electrons.
The 4f and 5d subshells are fully filled so those 
electrons are core electrons.
In the shorthand notation for electron 
configurations
all of the valence electrons from the noble gas 
the proceeds of the elements are core 
electrons.
So lead has four valence electrons and 78 core 
electrons.
Next let's determine how many core and 
valence electrons titanium has.
Based on the periodic table, titanium's electron 
configuration is Argon 4s2 3d2.
n=4 is the highest energy level so the two 
electrons and the 4s subshell are valence 
electrons.
Titanium is a transition metal and the 3d 
subshell is only partially filled 
so the two electrons in the 3d subshell are also 
valence electrons.
Since all of the electrons from the noble gas 
that precedes the element are core electrons,
titanium has four valence electrons and 18 core 
electrons.
