ELECTRON CONFIGURATIONS
 Orbital energies within a Principle Energy Level of multi
electron atoms are split.
 To create electron configurations or orbital box diagrams
for the ground state, to following considerations are
applied:
Aufbau Principle
 each additional added electron will occupy the lowest
available energy state.
Hund’s Rule
 electrons must be distributed among orbitals of equal
energy in such a way that as many electrons as possible
remain unpaired. eg. px then py then pz.
Pauli Exculsion Principle
 no 2 electrons within an atom may have the same
set of 4 quantum numbers.
eg. P [Ne] 3s2 3p3
P [Ne]   

S [Ne] 3s2 3p4
S [Ne]   

Ionic and Anomalous Configurations and
Magnetism
Ion Charges – are formed when:



the valence electrons are removed to obtain symmetrical
structures, like the noble gases with filled shells.
Transition elements can’t do this because of d electrons
Symmetry is obtained by having:
 fully-filled, half-filled and/or empty sub-shells.
 it is more stable to have a full (or half-full) d
sublevel than a full s sublevel
eg. Ag
[Ar] 4s2 3d9
Ag
[Ar]      
Ag should lose its 2 valence 4s
Ag2+ [Ar] 4s0 3d9
   
Ag2+ [Ar]
Actual
Ag1+ [Ar] 4s0 3d10
   
Ag1+ [Ar]

Not symmetrical

Symmetrical!
For metals under the metal/non-metal staircase:
eg. Pb
[Xe] 6s2 4f14 5d10 6p2
Pb2+ [Xe] 6s2 4f14 5d10
Pb4+ [Xe] 4f14 5d10
inner pair effect
Anomalous Configurations
 occur when the atom is unstable in the ground
state – several examples in the transition metals
 only need to know for 4U , Cr and Cu
Cr should be
Cr
[Ar] 4s2 3d4
Cr
[Ar]   


Actually exists as
Cr
[Ar] 4s1 3d5
 
Cr
[Ar] 


Similarly, Cu should be
Cu
[Ar] 4s2 3d9
Cu
[Ar]   
  
Actually exists as
Cr
[Ar] 4s1 3d10
 
Cr
[Ar] 
  

Explaining Magnetism
Ferromagnetic Elements – Fe, Co, Ni
 have 4,3,2 unpaired electrons with small, closely
packed atoms
 can form permanent “domains” where all the
atoms align their “north poles” in the same
direction
 can exist in the elements and also ionic
compounds of these metal ions
Paramagnetism
 due to unpaired electrons in electron
configuration
 can occur in atoms, molecules and ionic
compounds
 “domains” of atoms do not form, but atoms do
have a dipole moment and a magnetic field can
align these dipoles
 much less powerful than ferromagnetism