We Can Figure This Out.org
Virtual Lab: How Semiconductors and Transistors Work
University of Virginia
© 2003-Present, John C. Bean
This fifth electron is squeezed into a higher energy state. In fact, at normal temperatures, heat can provide it with enough energy that it can break away from the core of the phosphorus atom and jump to a neighboring silicon atom. From there, it can jump to other atoms.

However, as the extra electron moves away, it leaves behind a phosphorus atom with 15 protons and neutrons, but only 14 electrons. The phosphorus atom thus has ionized to a net +1 charge. This +1 charge pulls on the -1 charge of the wandering electron and forces it to stay in the general vicinity.

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