2 Electron basics Carries the negative charge of the atom Has mass of amu (6/10000 mass of a proton)Located in region around nucleusHas a spin that creates a magnetic fieldEither spins clockwise (“up”)Or counterclockwise (“down”)Atoms are electrically neutral, therefore, the number of electrons = number of protons.
3 B. Electron Placement1. Not Bohr OrbitsElectrons rarely, if ever, orbit in neatly defined circles.
4 2. Orbitals = Regions of Probability B. Electron Placement2. Orbitals = Regions of ProbabilityWhere electrons are likely to be foundDetermined by electron densityArea of high density = many electrons are there = Orbital!Area of low density = few electrons are there = Not Orbital!
5 2. Orbitals = Regions of Probability Orbital Shapes:f – very complex shapes, with seven orbital orientations. (pictures don’t do this shape justice.)d - clover shaped, with four possible orientations in xy, yz, zx, and x2 – y2 planes; also one dumb-bell-with-ring shape, on z-axis. Five total orbital orientations.s - spherical shape, centered on nucleusp - dumb-bell shaped, with three possible orientations on x-, y- or z-axes. Dumb-bell “neck” centers on nucleus
6 B. Electron Placement 3. Energy Levels Energy level Sublevels n = 1 1s As Bohr theorized, we believe electrons have certain levels of energy (level = n = 1, 2, 3, etc.)For each level of energy, there are sublevels of energy:Energy levelSublevelsn = 11sn = 22s, 2pn = 33s, 3p, 3dn = 44s, 4p, 4d, 4f
7 3. Energy Levels Each level n has n sublevels Each sublevel (s, p, d, f) corresponds to orbital shapes and orientations:Sublevel s contains one s orbitalSublevel p contains three p orbitalsSublevel d contains five d orbitalsSublevel f contains seven f orbitals
8 B. Electron Placement4. Fitting electrons into place: Electron ConfigurationAufbau Principle: Electrons will inhabit the lowest possible energy level and sublevel.Pauli Exclusion Principle: Each orbital holds a maximum of two electrons: one of each spin.Hund’s Rule: Electrons will spread themselves out in a sublevel so that a maximum number of unpaired electrons resultIf a sublevel were a bus, electrons wouldn’t share seats unless they had to.
9 Electron Configuration Y1s2s2p3s3p4s3dFluorine: 9 protons, 9 electrons1s22s22p5