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 valence 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 that precedes 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 in 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.