Question

A pentavalent impurity has ________Valence electrons

• A. 3
• B. 4
• C. 5
• D. 6

Answer 1

The correct option is C 5

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 pentavalent impurity has 5 valence electrons. When it is added, one atom of it forms bonds with four atoms of the semiconductor. Only four atoms are engaged in bonding. The fifth electron is free and available for conduction. Thus a pentavalent impurity adds a negative charge carrier (electron) and is also known as n-type impurity. A semiconductor with such an impurity is known as n-type semiconductor.