Download Electron Configuration

Electron Configuration
Order of Energy Levels




Inner shell electrons “shield” outer electrons
from the full positive effect of the nucleus –
“screening effect”
Different orbitals shield the outer electrons
more effectively than others
Not all orbitals experience the same + charge
from the nucleus
Therefore different orbitals have different
potential energies
Degenerate Orbitals

Orbitals that have the same energies
Electron Spin



Electron behaves as if it is spinning on
its axis
Fourth Quantum number (ms) is the
spin number
It can be either –1/2 or +1/2

Spinning electrons produce magnetic
fields
Pauli Exclusion Principle



No two electrons can have the same set
of four quantum numbers (n, l, ml, ms)
If an orbital has two electrons in it, they
must have different spins
Electrons in the same orbital with
different spins are called paired
electrons
Configuration


Arrangement of electrons in the atom
Aufbau Principle – orbitals fill in order of
increasing energy
Orbital Diagram of Li ( 3 e-)

1s22s1
Orbital Diagram of B (5 e-)

1s22s22p1
Hund’s Rule

Electrons occupy degenerate orbits
singly first
Orbital Diagram of C (6 e-)

1s22s22p2
Orbital Diagram of Ne (10 e-)

Configuration 1s22s22p6
Valence Electrons


Outer shell electrons
Ones in the last main energy level
▪ K

1s22s22p63s23p64s1
Fe 1s22s22p63s23p64s23d6
1 valence e
2 valence e