Donor impurities in silicon are elements that have one more valence electron than silicon (which has 4 valence electrons). These extra electrons are easily donated to the silicon lattice, increasing the number of free electrons and making the silicon n-type.

Here are some common donor impurities in silicon:

* Phosphorus (P): This is the most commonly used donor impurity. It has 5 valence electrons, contributing one extra electron to the silicon lattice.

* Arsenic (As): Similar to phosphorus, arsenic also has 5 valence electrons and acts as a donor impurity.

* Antimony (Sb): Antimony also has 5 valence electrons and is another common donor impurity.

These elements are typically added to silicon in very small quantities (parts per million or billion) to achieve the desired electrical conductivity.