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Pentavalent impurities Impurity atoms with \(5\) valence electrons produce \(n-\) type semiconductors by contributing extra electrons. Trivalentimpurities Impurity atoms with \(3\) valence electrons produce \(p\) - type semiconductors by producing a "hole" or electron deficiency. The trivalent and pantavalent atoms need an additional electron to form covalent bonds.