To explain the observed sequence 2, 8, 18, 32,..., of the number of electrons in filled atomic shells of the periodic table, one may argue as follows (which is not the text book explanation) starting from the structure of Helium as described in a previous post:
Helium has 2 electrons filling a K-shell of width 1/2. The next element in the table is Lithium with 2 electrons filling a K-shell of width 1/3 and 1 electron in an outer L-shell of width 1 being attracted by a net charge of +1 from the kernel and the two inner shell electrons. In the model I am studying in this sequence of posts, the 3rd electron of Lithium of width 1 being attracted by a net charge of +1 finds a relative energy minimum in a second shell outside an inner shell of diameter 1/2 filled by two electrons.
More generally, seeking the number of electrons $Z$ required to fill a 2nd L-shell we compute the radius d of the 2nd shell to be
- $d_2 = \frac{1}{Z+2} + \frac{1}{Z}$
- $A = 4 \pi \times d_2^2$ .
- $Z\times 2\pi\times\frac{1}{Z^2}$.
- $4\times\pi\times(\frac{1}{Z+2} + \frac{1}{Z})^2 = 2\pi\times\frac{1}{Z}$
- $2\times (\frac{2}{Z})^2 = \frac{1}{Z}$
- $2\times (\frac{3}{Z})^2 = \frac{1}{Z}$
- $Z(N) = 2 \times N^2$.
PS1 The simple shell model under study gives the following ground state energy $E$ for Neon with $N = 2$ and $2 + 8 = 10$ electrons:
- E = - 2 x 10/(1/10) + 1/(1/10)^2 + 1/(2/10) - 8 x 8/d_e + 8/2 x 1/(1/8)^2 + E_e
- d_2 = 1/10 + 1/16
- E_e = 8 x 7/2 x 1/d_e
- d_e = 2 x 1/8
- E = - 95 - 393 + 256 + 112 = - 119
PS2 For Carbon with 2 + 4 = 6 electrons we get similarly
- E = [- 2 x 6/(1/6) + 1/(1/6)^2 + 1/(2/6)] + [- 4 x 4/(1/6 + 1/8) + 4/2 x 1/(1/4)^2 + 4 x 3/2 x 1/(1/2)]
- = [- 72 + 36 + 3] + [- 55 + 32 + 12] = - 33 - 11 = - 44
PS3 For Oxygen O with 2 + 6 = 8 electrons, we get similarly:
- E = [- 2 x 8/(1/8) + 1/(1/8)^2 + 1/(2/8)] + [- 6 x 6/(1/8 + 1/12) + 6/2 x 1/(1/6)^2+6 x 5/2 x 1/(1/3)]
- = [- 128 + 64 + 4] + [- 178 + 108 + 45] = - 59 - 25 = - 84


Inga kommentarer:
Skicka en kommentar