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6 Atomic Concepts Subatomic Particles Charge Mass proton + 1 1 amu electron – 1 1/1836 neutron 0 1 Location atomic mass number (#p + #n) nucleus orbits nucleus atomic number 12.011 C (#p) 6p+ 6e ---------------------------------------------------◦ (#n) 6n NOTE: charge of nucleus = #p Isotopes – atoms of the same element, which differ in the number of neutrons; have the same atomic no., but a different mass number 12.0000 13.0335 C 6p+ 6e - -------------------◦ 6n WEIGHTED AVERAGE ATOMIC MASS C 6p+ 6e - 0.9889 (12.000) + 0.0111(13.0335) = 12.011 amu The atomic mass will be closest to the isotope with the greatest percentage. -----------------◦ 7n relative abundance: 98.89% - 1.11% Electron Configuration – the arrangement of electrons in the energy levels (orbits, shells) of an atom in the ground state. ___________ distance from nucleus, ___________ energy of electron In the ground state, electrons fill the lowest available energy level, starting from the shell closest to the nucleus. Complete Energy Levels: 2-8-18-32 …. 8 max “valence” e---------------------------------------------------------------------------------------------------------------------------- 7 “Ground State” Possible “Excited State”- move only one e further away from - nucleus 2-8-3 2-7-4 or 2-8-2-1 or 1-8-4 , but not 3-7-3 Metals- lose electrons forming (+) ions Na 2-8-1 Na +1 2-8 Nonmetals – gain electrons forming (-) ions O-2 O 2-6 2-8 The ions have a “Noble Gas” electron configuration = 8 electrons in the outermost shell. Lewis (e- Dot) Structure – represents only the valence electrons; start with the first 2 dots together in the 12 o’clock position, continue placing electrons in the remaining positions (3, 6 & 9 o’clock), one at a time, until you have two in each; the max is an OCTET. Rutherford’s Gold Foil Experiment An atom is mostly “empty” space; its “nucleus” is very small, but massive, and it’s positively charged. Wave Mechanical Model for explaining spectra of elements with multi-electron atoms Orbital – the region around the nucleus of an atom where an electron can most probably be found; aka “electron cloud”.