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Orbital Notation and Electron Configuration October 20th Distance From The Nucleus Called the Principle Quantum Number (n) Describes the principle energy level n = 1, 2, 3 Shape of the Orbital Described by Orbital quantum number (l) Tells you the shape of the orbital the electron is in Is it an s, p, d, or f orbital? Position in 3D Space Described by Magnetic Quantum Number (m) Indicated the position of the orbital around the 3 axes (x, y, z) Electron’s Spin The direction of the electron’s spin is described by the spin quantum number Electrons can be either up or down When electrons are part of a pair, they must spin in opposite directions Pauli Exclusion Principle No two electrons in the same atom can have the same four quantum numbers (the same description) No two electrons can have the same address Electrons are repulsed by each other, so they cannot live together… Hence makes sense they have opposite spins! Review Of Energy Levels n=1 s orbital (2 electrons) n=2 s orbital (2 electrons) p orbital (6 electrons) n=3 s orbital (2 electrons) p orbital (6 electrons) d orbital (10 electrons) n=4 s orbital (2 electrons) p orbital (6 electrons) d orbital (10 electrons) f orbital (14 electrons) 3 Rules for Electron Configuration 1) Aufbau Principle - electrons occupy the orbitals of lowest energy first 2) Pauli Exclusion Principle - no two electrons can have the same address(same 4 quantum #s) 3) Hund’s Rule - Electrons try to occupy different orbitals before pairing up Orbital Notation order in which electrons are filled The Order in which orbitals fill… Orbital Notation ORBITAL BOX NOTATION for He, atomic number = 2 Arrows 2 depict electron spin 1s 1s Arrangement of Electrons in Atoms Each orbital can be assigned no more than 2 electrons! Each orbital can hold a pair of electrons per orientation s 1 orientation(pair) 2 electrons p 3 orientations 6 electrons d 5 orientations 10 electrons f 7 orientations 14 electrons Orbital Diagram _____ 1s _____ 2s _____ _____ _____ 2px 2py 2pz _____ 3s _____ _____ _____ 3px 3py 3pz _____ _____ _____ _____ _____ 3d _____ 4s _____ _____ _____ 4px 4py 4pz _____ _____ _____ _____ _____ 4d _____ 5s _____ _____ _____ 5px 5py 5pz _____ _____ _____ _____ _____ 5d _____ 6s How Orbitals Fill…. _____ 1s _____ 2s _____ _____ _____ 2px 2py 2pz _____ 3s _____ _____ _____ 3px 3py 3pz Electron Configuration – Strontium _____ 1s _____ 2s _____ _____ _____ 2px 2py 2pz _____ 3s _____ _____ _____ 3px 3py 3pz _____ _____ _____ _____ _____ 3d _____ 4s _____ _____ _____ 4px 4py 4pz _____ _____ _____ _____ _____ 4d _____ 5s _____ _____ _____ 5px 5py 5pz _____ _____ _____ _____ _____ 5d _____ 6s Valence electrons are electrons in the outermost energy level of an atom. Example: Sulfur _____ 1s _____ 2s _____ _____ _____ 2px 2py 2pz _____ 3s _____ _____ _____ 3px 3py 3pz Valence electrons Practice on your own! Draw the orbital diagram for Calcium Draw the orbital diagram for Silicon Electron Configuration for H, atomic number = 1 1 s 1 Energy Level no. of electrons Subshell (s, p, d, f) Electron Configuration Fortunately! Its like orbital diagrams but without drawing the orbitals… Fill electrons into lower energy levels first Follow order of filling Remember how many electrons each level can hold: s holds 2, p holds 6, d 10, f 14 Examples Helium: 1s2 Boron : 1s22s22p1 Magnesium: 1s22s22p63s2 Bromine: 1s22s22p63s23p64s23d104p5 Practice on your own! Hydrogen 1s1 Sodium 1s22s22p63s1 Magnesium 1s22s22p63s2 Chlorine 1s22s22p63s23p5 Argon 1s22s22p63s23p6 Arsenic 1s22s22p63s23p64s23d104p3 Octet Rule Octet rule - all elements want to have a full set of valence electrons Atoms will lose or gain electrons in trying to achieve a full octet Octet Rule Octet Rule states that atoms will gain or lose electrons to achieve a full outermost energy level. This is usually 8 electrons (s2 p6). Example: Oxygen _____ 1s _____ 2s O _____ _____ _____ 2px 2py 2pz
