Wednesday September 30, 2009

The Schrondinger Wave Equation

• Electrons do not travel around the nucleus in neat orbits, as Bohr had postulated.
• Instead, they exist in certain regions called orbitals.
• An orbital is a three-dimensional region around the nucleus that indicates the probably location of an electron.

Remember! Dr. B said that she did NOT like the use of the word orbital. Do not think of them as neat train tracks but as a volume.

Atomic orbitals and Quantum numbers

• Quantum numbers specify the proterties of atomic orbitals and the properties of electrons in orbitals.
• The principle quantum number, symbolized by n, indicates the main energy level occupied by the electron.
• The angular momentum quantum number, symbolized by a lower-case L (she likes it in cursive), indicates the shape of the orbital.
• The magnetic quantum number, symbolized by m, indicates the orientation of an orbital around the nucleus.
• The spin quantum number (s) has only two possible values, +1/2 or -1/2, which indicates the two fundamental spin states of an electron in an orbital.

Here is a chart she put up on the board which helps clarify the meaning of this.


Principal Quantum Number
Energy n= 1,2,3,...
Angular l= 0,1,2...n-1
Magnetic m= -l...0...+l
Spin s= +1/2, -1/2

Here are some Sample problems we did in Class illustrating this.

N=1 then
l=0 then
m=0 then
s=+1/2,-1/2
The total number of electrons is 2 (2e-)
This is actually the first row in the Periodic Table!.... hooray...?

Here is another.
N=2 then
l=0 or 1 then
m=0
s=+1/2,-1/2
Thus we have 2e- + 6e- which = 8e-.
If you are still not quite sure what happened, check out the diagrams in your books.
As a matter of fact, I will just give you a free one right here.


Quantum Numbers of the first 30 atomic orbitals

n l m orbital names Number 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

The s,p,l,f,g are the sub-level orbitals

Electron Configurations

• The arrangement of electrons in an atom is known as the atom's electron configuration.
• The lowest-energy arrangement of the electrons for each element is called the element's ground-state electron, configuration.

Don't forget that Dr. B expects everyone to have finished the chapter by Thursday! (we are in section 3 right now)

Also in as a side note, Dr. B has not given a quiz for a while now, it would probably a good idea to start preparing for a very possible not to mention probable pop quiz.

Have a good day!