Question

A trivalent impurity has ______ valence electrons

• A. 4
• B. 5
• C. 6
• D. 3

Answer 1

The correct option is D 3

In a pure semiconductor, each atom is surrounded by four atoms and is engaged in chemical bond with all of them. This is because a pure semiconductor has four valence electrons. A trivalent impurity has 3 valence electrons. When it is added, one atom of it forms bonds with three atoms of the semiconductor. Only three atoms are engaged in bonding. There is an empty space between the atom of impurity and the fourth atom of pure semiconductor. Such an empty space is called as hole which is available for conduction.