- #1
mk_gm1
- 10
- 0
Let's say I'm considering the [tex]3p^2[/tex] electrons. From the Pauli Exclusion Principle, we know that two electrons cannot have the same state, which in this case means ml and ms cannot both be the same for each electron.
What this means is that the following 6 terms must not be allowed:
[tex]m_{l1} \hspace{0.1 in} m_{l2} \hspace{0.1 in} m_{s1} \hspace{0.1 in} m_{s2}[/tex]
[tex]-1 \hspace{0.1 in} -1 \hspace{0.1 in} \downarrow \hspace{0.3 in} \downarrow[/tex]
[tex]-1 \hspace{0.1 in} -1 \hspace{0.1 in} \uparrow \hspace{0.3 in} \uparrow[/tex]
[tex]0 \hspace{0.4 in} 0 \hspace{0.3 in} \downarrow \hspace{0.3 in} \downarrow[/tex]
[tex]0 \hspace{0.4 in} 0 \hspace{0.3 in} \uparrow \hspace{0.3 in} \uparrow[/tex]
[tex]+1 \hspace{0.1 in} +1 \hspace{0.1 in} \downarrow \hspace{0.3 in} \downarrow[/tex]
[tex]+1 \hspace{0.1 in} +1 \hspace{0.1 in} \uparrow \hspace{0.3 in} \uparrow[/tex]
These correspond to [tex]M_L=\sum m_{li}
= -2, -2, 0, 0, 2, 2[/tex] and [tex]M_S = \sum m_{si} = -1, 1, -1, 1, -1, 1[/tex] respectively.
My question is this - how does this lead to the conclusion that the allowed terms are 1S, 1D and 3P ? For example, there's a ML = 0, MS= -1 term in both 3S and 3P - why do we disallow one and not the other?
Also, what leads us to disallow 1P (for which ML=-1, 0, 1 and MS=0)? Surely the only way to have MS = 0 is to have [tex]\downarrow_1 \hspace{0.1 in} \uparrow_2[/tex] or vice versa, and hence [tex]m_{s1} \neq m_{s2}[/tex] and we have no violation of the Pauli Exclusion Principle?
What this means is that the following 6 terms must not be allowed:
[tex]m_{l1} \hspace{0.1 in} m_{l2} \hspace{0.1 in} m_{s1} \hspace{0.1 in} m_{s2}[/tex]
[tex]-1 \hspace{0.1 in} -1 \hspace{0.1 in} \downarrow \hspace{0.3 in} \downarrow[/tex]
[tex]-1 \hspace{0.1 in} -1 \hspace{0.1 in} \uparrow \hspace{0.3 in} \uparrow[/tex]
[tex]0 \hspace{0.4 in} 0 \hspace{0.3 in} \downarrow \hspace{0.3 in} \downarrow[/tex]
[tex]0 \hspace{0.4 in} 0 \hspace{0.3 in} \uparrow \hspace{0.3 in} \uparrow[/tex]
[tex]+1 \hspace{0.1 in} +1 \hspace{0.1 in} \downarrow \hspace{0.3 in} \downarrow[/tex]
[tex]+1 \hspace{0.1 in} +1 \hspace{0.1 in} \uparrow \hspace{0.3 in} \uparrow[/tex]
These correspond to [tex]M_L=\sum m_{li}
= -2, -2, 0, 0, 2, 2[/tex] and [tex]M_S = \sum m_{si} = -1, 1, -1, 1, -1, 1[/tex] respectively.
My question is this - how does this lead to the conclusion that the allowed terms are 1S, 1D and 3P ? For example, there's a ML = 0, MS= -1 term in both 3S and 3P - why do we disallow one and not the other?
Also, what leads us to disallow 1P (for which ML=-1, 0, 1 and MS=0)? Surely the only way to have MS = 0 is to have [tex]\downarrow_1 \hspace{0.1 in} \uparrow_2[/tex] or vice versa, and hence [tex]m_{s1} \neq m_{s2}[/tex] and we have no violation of the Pauli Exclusion Principle?