4.10 – NOTES Electron Configurations Part 2

Electron Configuration and the Periodic Table

Example Uranium Electron Configuration:

C. Abbreviated Electron Configurations 1. Noble Gas Inner Core – a complete set of orbitals (full s and p) is representative of a noble gas - the noble gas can then be used as an abbreviation; the symbol of the noble gas must be placed in [ ] and then the e- config will start with the next energy level and continue from there; must always work forwards, can NOT go backwards i.e. – Te would start with Kr and not Xe

2. Examples Orbital Electron Configuration Uranium -   Tungsten -

D. Exceptions to the aufbau principle d-block orbitals have incompletely filled subshells and readily give rise to cations that have completely filled shells; different configurations due to closeness of 3d and 4s orbital energies; as move to the right the nuclear charge increases, [Ar] pulls core e- tighter, d level becomes more stable Cr = [Ar]4s13d5 NOT 4s23d4 Cu = [Ar]4s13d10 NOT 4s23d9 Mo = [Kr]5s14d5 Ag = [Kr]5s14d10 Au = [Xe]6s14f145d10

E. Valence electrons 1. Definition - outermost electrons involved in the bonding process - similarity of outer electron configurations is what gives elements in a family the same chemical behavior; have to be somewhat careful b/c slow change in metals  nonmetals for groups 3A-8A

2. Electron-dot structures - only apply to groups 1, 2, 13-18 - dot represents valence electron - must follow Hund’s rule  pair the first two (s orbital), don’t pair the remaining three sides until forced to do so (p orbital)

Li As   Mg S Al F Sn Ar