Question

p type semi conductor is formed when trace amount of impurity is added to silicon. The number of valence electron in the impurity atom must be
a) 3
b) 5
c) 1
d) 2

Answer 1

The answer will be 3. You can take the example of Ge+ which will require trivalent sort of impurity to convert into the p-type semiconductor.

However, it can be different for different material but mainly it is used for the trivalent impurity only so that the semiconductors can be formed easily.