Orbital Filling

1
Orbital Filling

• Energy levels around the nucleus are numbered 1-7
  
• 1 being closest to the nucleus
• (the lowest energy)
• 7 being furthest away from the nucleus
• (the highest energy)
• For simplicitys sake like concentric rings
  around a central sphere

2
Orbital Filling

• Each level contains sublevels
• s(2 e max), p(6 e max), d(10 e max), f(14 e max)
• in the following fashion
• Nucleus (protons/neutrons)
• 1s
• 2s 2p
• 3s 3p 3d
• 4s 4p 4d 4f
• 5s 5p 5d 5f
• 6s 6p 6d
• 7s 7p

3

• Electrons fill the orbitals from lowest to
  highest energies
• It would make perfect sense if all the 1 orbitals
  were filled, followed by the 2 orbitals, then all
  the 3 orbitals, and the 4 and 5 and so on, BUT
  THAT IS NOT TRUE
• However, there is a pattern that orbital filling
  follows and there are several shortcuts to
  remembering the order (instead of memorizing)

4
1s2s2p3s3p4s3d4p5s4d5p6s4f5d6p7s5f6d7p

• This is one method
• Write the levels 1-7 in descending order with
  their corresponding sublevels.
• Follow the arrows, also in descending order, to
  show the pattern of orbital filling

5

• The diagram shows that electrons will fill the 4s
  orbital before filling the 3d orbital.
• Indicating that the 4s orbital is at a lower
  energy level than the 3d orbital.
• Even the 6s orbital is filled (lower energy
  level) before the 4f orbital (higher energy level)

6
Electron Configuration

• What is the electron configuration for Fe (AN
  26)?
• 1s22s22p63s23p64s23d6
• Or Ne3s23p64s23d6
• Or Ar 4s23d6
• Putting the order as 1s22s22p63s23p63d64s2 would
  be incorrect because that order says that the 3d
  orbital fills before the 4s orbital, but we
  understand that the 4s orbital is lower in energy
  and thus fills first
• What is the electron configuration for Cl (AN
  17)?
• 1s22s22p63s23p5 -or- Ne3s23p5

7
1 s
2 s
--------------2 p------------
3 s
--------------3 p------------
4 s
--------------4 p------------
------------------------3 d----------------------
-
5 s
--------------5 p------------
------------------------4 d----------------------
-
6 s
--------------6 p------------
------------------------5 d----------------------
-
7 s
------------------------6 d----------------------
-
------------------------------------4
f-----------------------------------
------------------------------------5
f-----------------------------------
8
reference

• http//www.steve.gb.com/science/atomic_structure.h
  tml
• http//sun.menloschool.org/dspence/chemistry/atom
  ic/config2.html