Download Writing Electron Configuration

Writing Electron Configuration
Quantum Numbers
Quantum numbers define the location of
electrons in an atomic orbital.
This helps us understand why different
atoms exhibit certain properties, such
as size and reactivity.
Quantum numbers are written like this:
(2,1,-1,-½) where (n, /, m/, ms)
They are like an “address”
n = main energy level
(principal quantum number)
/ = orbital shape
(angular momentum quantum number)
m/ = orientation of orbital
(magnetic quantum number)
ms = electron spin
(spin quantum number)
Quantum Numbers for the First 30 Orbitals
n (1, 2, …) / (0, 1,…n-1)
m (or m/)
-/ to +/
Orbital
name
# of orbitals
1
0
0
1s
1
2
0
0
2s
1
2
1
-1,0,1
2p
3
3
0
0
3s
1
3
1
-1,0,1
3p
3
3
2
-2, -1,0,1, 2
3d
5
4
0
0
4s
1
4
1
-1,0,1
4p
3
4
2
-2, -1,0,1, 2
4d
5
4
3
-3 -2, -1,0,1, 2, 3
4f
7
Writing Electron Configuration
It’s useful to be able to write out the
location of electrons in an atom.
Si: 1s2, 2s2, 2p6, 3s2, 3p2
There are three rules that govern electron
configuration.
Aufbau Principle
• “Aufbau” is German for building up.
• Each electron occupies lowest energy
state available
• Energy states roughly relate to period.
Memorizing Orbital Filling Order
Pauli Exclusion Principle
• No two electrons may have the same 4
quantum numbers.
• This means:
• Maximum of 2 electrons occupy a single
atomic orbital
• The 2 electrons must have opposite
spins, represented by up/down arrows.
Hund’s Rule
• Each equal-energy orbital gets one
helping of electron before any orbital
gets a second helping.
• This is evident in Orbital Diagrams
Orbital Diagrams