setTitle('Semiconductors'); ?> setMetaKeywords('Physics, Semiconductors, Solid State Physics, Doping, N-doping, P-doping, Silicon, Germanium, Transistors, William Shockley, John Bardeen, Walter Brattain, Jack Kilby, Nobel, Prize, Laureate, Robert Noyce, Chip, Integrated Circuit, Conduction, Band Gap, Band, Bands, Shell, Energy, Valence, Atomic Structure, Electron-Hole, Hole, Extrinsic, Intrinsic'); ?> setMetaDescription('Nobelprize.org, Official web site of the Nobel Foundation'); ?> setCssIncludes('++/css/bare.css'); ?> printHeader('top_bare.php'); ?>

10:25


	Shells and Energy Levels
	Each atom has a fixed number of electrons. Silicon, for instance, has fourteen of them. These electrons are divided into shells (orbits), depending on their energy. The closer the electrons are to the center of the atom, the lower their energy. This means that the electrons fill the shells of the atom from the bottom up. The highest shell in an atom occupied with electrons is called the valence shell. The electrons in the valence shell are called valence electrons. Note that the valence shell is not the outermost of all shells, it is just the outmost shell occupied with electrons. There are still empty shells outside it.

printFooter('bottom_bare.php'); ?>