
Principles of Analog Electronics
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Arsenic, for example, is a pentavalent element, that is, with ve valence electrons
(more specically at the level M, n = 3, it has two electrons in the subshell s and
three in the subshell p). Therefore it has 1 electron more than necessary to satisfy
the octet rule of the subshell p of the level n = 3 of silicon. This is why arsenic and
silicon do not form a natural chemical bond, but it is articially made by implan-
tation. Added arsenic atoms furnish four valence electrons each to complete the
valence level of silicon atoms, plus one extra electron not necessary for valence
bonds, so useful to become a ...