# C, Si and Ge atoms have 4 Valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by $E_C, E_{Si}, E_{Ge}$ respectively. Which of the following relationship is true in their case?

The 4 bonding electrons of C, Si or Ge lie, respectively, in the second, third and fourth orbit. Hence, energy required to take out an electron from these atoms (i.e., ionisation energy) will be least for Ge, followed by Si and highest for C. Hence, number of free electrons for conduction in Ge and Si are significant but negligibly small for C.
$\Rightarrow E_C \gt E_{Si} \gt E_{Ge}$