The excited state electron configuration of one atom shows the promotion of a valence electron come a greater energy state.

You are watching: Which electron configuration represents the electrons of an atom in an excited state?


An electron construction representing an atom in the excited state will show a valence electron advocated to a higher energy level.

ExampleThe ground state electron construction of sodium is #"1s"^2"2s"^2"2p"^6"3s"^1#.

In the excited state, the valence electron in the #"3s"# sublevel is advocated to the #"3p"# sublevel, offering the electron construction as#"1s"^2"2s"^2"2p"^6"3p"^1#.

This is a an extremely unstable condition and also the excited electron will drop earlier down to the #"3s"# sublevel, releasing the same amount of power that was absorbed, and producing a characteristic shade of light, in this case yellow.


Answer connect
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Truong-Son N.
january 14, 2016

The very first excited state is the same configuration as the ground state, other than for the place of one electron.

As one example, sodium goes with a #3s -> 3p# transition.

The ground state electron construction for sodium is:

#color(blue)(1s^2 2s^2 2p^6 3s^1)#

And the first excited state electron construction for salt is:

#color(blue)(1s^2 2s^2 2p^6 3p^1)#

This coincides to an excitation come a very first excited state the is less stable; the then leads to a relaxation back down to the floor state. The be sure emits yellow light (#"589 nm"#).

I finish up walk through selection rules (which help you predict whether an electronic transition is permitted or forbidden), ax symbols, and also predicting transitions. That overall tells you just how I know that a #3s -> 3p# transition is a real change for sodium.

(If you want, you deserve to skip the term symbols contextual section; it"s optional.)

You may or may not have learned selection rules yet, however they aren"t too daunting to take note of. Lock would assist you determine exactly how to create electron configurations because that excited states.

SELECTION RULES

The an option rules govern how an electron is observed to shift (excite upwards or relax downwards) native one orbit to another.

Formally, they space written as:

#color(blue)(DeltaS = 0)##color(blue)(DeltaL = 0, pm1)#

#color(blue)(L + S = J)#

#:. Color(blue)(DeltaJ = 0, pm1)#

where #DeltaS# is the change in intrinsic angular momentum of the electron (spin multiplicity is #2S + 1#), #DeltaL# is the adjust in orbital angular momentum, and #DeltaJ# is the change in the total angular momentum.

It is useful to know the an option rules if you desire to predict exactly how an excited state configuration have the right to be written just based on the atom"s (correct) ground state configuration.

EXAMPLES OF digital EXCITATION TRANSITIONS

Allowed:

An instance of an allowed digital transition upwards that one unpaired electron to an north orbital:

#color(green)(2s -> 2p)# (#color(green)(DeltaS = 0#, #color(green)(DeltaL = +1)#, #color(green)(DeltaJ = 0, pm1)#)

#DeltaL = +1# due to the fact that for #s#, #l = 0#, and also for #p#, #l = 1#. Thus, #DeltaL = +1#.

#DeltaS = 0# because the electron didn"t acquire paired through any brand-new electron. It began out unpaired, and also it stayed unpaired (#m_s^"new" = m_s^"old"#), so #DeltaS = m_s^"new" - m_s^"old" = 0#.

Forbidden:

An instance of a forbidden electronic transition upwards the one unpaired electron to an empty orbital:

#color(green)(3s -> 3d)# (#color(green)(DeltaS = 0)#, #color(green)(DeltaL = color(red)(+2))#, #color(green)(DeltaJ = 0, pm1, color(red)(pm2))#)

#DeltaL = +2# due to the fact that for #s#, #l = 0#, and for #d#, #l = 2#. Thus, #DeltaL = +2#, which is larger than is allowed, so it is forbidden.

#DeltaS# is tho #0# since it"s the exact same electron transitioning as before, simply towards a different orbital.

TERM symbols / CONTEXT

"I"ve never ever seen #L#, #S#, or #J# before. Huh? What room they supplied for?"

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DISCLAIMER: The over link explains term signs for context. It help to understand this, but you don"t need to know this prefer the earlier of her hand unless you room taking physical Chemistry.

APPLICATION the THE selection RULES

Alright, therefore let"s use the selection rules themselves. I gave examples already, therefore let"s work-related off of the allowed transition example and change it a small bit. The worths for #L#, #S#, and #J# are pretty similar.

Let us research this energy level diagram because that sodium:

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You deserve to see lines on the diagram going indigenous the #3s# orbit to 2 #3p# orbital destinations. That suggests either an excitation from the #3s# come the #3p# or a relaxation indigenous the #3p# come the #3s#.

These 2 lines are marked #589.6# and #589.0#, respectively, in #"nm"#, therefore what you view happening is that sodium provides its #"589 nm"# excitation transition (upwards), and then relaxes (downwards) come emit yellow light.

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Therefore, a typical excitation/relaxation change sodium renders is:

Excitation Transition: #3s -> 3p# (#DeltaS = 0#, #DeltaL = +1#, #DeltaJ = 0, +1#)

Relaxation Transition: #3p -> 3s# (#DeltaS = 0#, #DeltaL = -1#, #DeltaJ = 0, -1#)

(Term symbol notation:

#""^2 S_"1/2" -> ""^2 P_"1/2", ""^2 P_"3/2"#, excitation

#""^2 P_"1/2", ""^2 P_"3/2" -> ""^2 S_"1/2"#, relaxation)

So the ground state electron construction for salt is:

#color(blue)(1s^2 2s^2 2p^6 3s^1)#

And the first excited state electron configuration for sodium is:

#color(blue)(1s^2 2s^2 2p^6 3p^1)#

Lastly, one easy way to mental what transitions are permitted is to keep in mind that electronic transitions on power level diagrams space diagonal, and also involves adjacent columns.