What are valence electrons?

We have valence electrons and conduction electrons in a semiconductor. Do we also have "valence holes" and "conduction holes"?

What are free electrons ?

C,Si and Ge have same of valence electrons.C is an insulator because energy required to take electron out from.

Statement I : In sulphur hexafluoride, the central atom has more than eight valence electrons. Statement II: The central atom can accommodate additional electron pairs by using outer vacant d orbitals.

Carbon, silicon and germanium have four valence electrons each . These are characterised by valence and conduction bands separated by energy band gap respectively equal to (E_(g))_(C) , (E_(g))_(Si) and (E_(g))_(Ge) . Which of the following statements is true ?

The sharing of valence electrons between the atoms will lead to the formation of_________