The arrangement of electrons in a lithium atom
Lithium (Li) has an atomic number of 3, meaning that in a neutral atom, the number of electrons will be 3. The energy levels are shown as concentric circles around the central nucleus, and the electrons are placed from the inside out. The first two electrons are found in the first energy level, and the third electron is found in the second energy level.
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"Free High School Science Texts Project, The Atom: Energy Quantisation and Electron Configuration. October 15, 2012."
http://cnx.org/content/m39967/latest/
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