The Electron Configuration

Write the electron configuration for a variety of atoms and ions Relate the electron configuration of an element to its valence electron(s) and its position on the periodic table. Additional KEY Terms Shorthand notation

NUCLEUS 1s 2s 2p 3s 3p 3d 4s 4p4d 4f Quantum Level ShapesTotal Orbitals 1s1s = 1 2s,p1s+3p = 4 3s,p,d1s+3p+5d = 9 4s,p,d,f1s+3p+5d+7f = 16 nn typesn2n2

1. Pauli Exclusion Principle Electrons are constantly spinning which creates a magnetic field Two electrons can occupy the same orbital only if they have opposite spins Each orbital (m) of a shape can hold two spinning electrons (s)

n = 1 1s 2 n = 2 2s 2 2p 6 n = 3 3s 2 3p 6 3d 10 OLD way NEW way 2e - 8e - 18e - 8e - 2e -

Quantum Level ShapesTotal orbitalse - capacity 1s1 = 12 2s,p1+3 = 48 3s,p,d1+3+5 = 918 4s,p,d,f = 1632 nn typesn2n2 2n 2

2. Aufbau Principle Unexcited electrons fill the lowest, most stable, energy orbital available – ground state. Notice: as you get further from the nucleus the energy differences are similar enough to mess-up the “order”

3. Hund rule Electrons must enter empty orbitals of equal energy first before joining occupied orbitals. The “get your own room” principle – no one wants a bunkmate

Electron Configuration Orbital Box Diagrams 1s2s 2p3s 3p 3d 4s These are the two ways of representing electron location – we will focus on Electron Configuration

Periodic Table shows orbital filling for the electron configuration of elements.

Draw orbital box and electron config for carbon. C: 1s 2 2s 2 2p 2 1s2s 2p Draw orbital box and electron config for Mg. Mg: 1s 2 2s 2 2p 6 3s 2 1s2s 2p3s First ask yourself “how many total electrons,” then put them in their correct orbitals

Draw electron config for germanium. Ge – atomic number 32 Ge: 4s 2 3d 10 4p 2 Shorthand notation using noble gas “kernels.” Ge: [Ar] 4s 2 3d 10 4p 2 1s 2 2s 2 2p 6 3s 2 3p 6 [Ar]

Write the shorthand configurations for Mn and Ag. Mn: [Ar] 4s 2 3d 5 Ag: [Kr] 5s 2 4d 9 Find the last filled Noble Gas to use as the kernel

Valence configuration includes the electrons in the outer-most or highest quantum level (n). F = 9 electrons 1s 2 2s 2 2p 5 Valence configuration - 2s 2 2p 5 Ge = 32 electrons 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 2 Valence configuration - 4s 2 4p 2 It’s not just the last ones, but the total electrons in the outer quantum level

F -1 = 9 electrons + 1 gained The ION configuration is 1s 2 2s 2 2p 6 Fe +2 = 26 electrons – 2 lost The ION configuration is 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 Valence electrons are removed from the highest quantum level 1s 2 2s 2 2p 5 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6

Some exceptions to the rule:

Half-filled and completely filled orbitals have extra stability Atoms will “promote” electrons to improve overall stability Electron Promotion Look for configurations ending in “p 2”,“p 5” OR “d 4”,“d 9” - one electron from being half or complete filled… ”

Cr: [Ar] 4s 2 3d 4 Cu: [Ar] 4s 2 3d 9 Actual configurations: Cr: [Ar] 4s 1 3d 5 Cu: [Ar] 4s 1 3d 10 4s 3d 4s 3d Electron promotion accounts for multiple ionization states (Fe +2, Fe +3 …)

CAN YOU / HAVE YOU? Write the electron configuration or orbital box diagrams for a variety of atoms and ions Relate the electron configuration of an element to its valence electron(s) and its position on the periodic table. Additional KEY Terms Shorthand notation