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Lesson 2.5 Describing the Electron’s Location



First Quantum Number (actually a letter)  n

[like the “country”]

- Whole numbers to describe the energy levels of electrons, ground state=1 Each energy level has a letter n= 1,2,3,4,5   and infinity

note n=1 is the ground state


Second Quantum Number  (l)  


- this letter designates the shape of the orbital

 s = spherical

p = double lobes (dumbbells)

d = ring and lobe

f = four lobe



Third Quantum Number    ml


This subscript describes the orientation in space of the orbit.


Fouth Quantum Number   ms


In the 1950’s, Wolfgang Pauli (Austalian) said electrons spin, producing a small magnetic field.

 An electron can spin clockwise or counterclockwise, designated + ˝  or - ˝.   

Only allowed two electrons per orbital, they spin opposite to each other.



Heath p. 294  Q # 2,4,7,8,9,10,11



2.  an energy level is a location of where the electron PROBABLY (mostly) spends most of its time and the levels start closest to the nucleus and get further away ….

Quantized means the levels go up in steps or certain amounts


4.  “a region of space, with a shape,(s, p, d , f) surrounding nucleus in which an electron will most probably be found”  = ORBITAL



7.  3 is higher than 2… therefore farther away from the nucleus


8.  It must absorb energy of a specific E,v,λ.


9.  Remember the electron spends most of its time in the sphere but could be found in another location.


10.  QM involves waves, mathematics, uncertainties,


11.  The first three Quantum numbers ..

    n  =  energy level

    l  =  Shape (s,p,d)

    ml = orientation (x,y,z)

    all of these will give you one unique orbital

an orbital is defined uniquely by the first 3 QN’s

an electron needs a fourth Q.N. (spin +- ˝) because 2 electrons can fit into the same orbital.