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

You are watching: Which electron configuration represents an atom in an excited state


An electron construction representing an atom in the excited state will present a valence electron promoted to a greater energy level.

ExampleThe floor state electron configuration of salt is #\"1s\"^2\"2s\"^2\"2p\"^6\"3s\"^1#.

In that excited state, the valence electron in the #\"3s\"# sublevel is supported to the #\"3p\"# sublevel, giving the electron configuration as#\"1s\"^2\"2s\"^2\"2p\"^6\"3p\"^1#.

This is a really unstable condition and the excited electron will drop back down come the #\"3s\"# sublevel, release the same amount of energy that to be absorbed, and also producing a characteristic color of light, in this case yellow.


Answer attach
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Truong-Son N.
jan 14, 2016

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

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

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 salt is:

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

This synchronizes to an excitation to a an initial excited state that is less stable; that then leader to a relaxation back down come the floor state. The be safe emits yellow light (#\"589 nm\"#).

I end up going through selection rules (which assist you predict even if it is an electronic transition is permitted or forbidden), term symbols, and predicting transitions. That as whole tells you exactly how I recognize that a #3s -> 3p# change is a real shift for sodium.

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

You might or might not have learned selection rules yet, but they aren\"t too difficult to take keep in mind of. Lock would help you determine exactly how to compose electron configurations because that excited states.

SELECTION RULES

The an option rules govern exactly how an electron is observed to shift (excite upwards or relax downwards) indigenous 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 readjust in intrinsic angular momentum that the electron (spin multiplicity is #2S + 1#), #DeltaL# is the readjust in orbital angular momentum, and #DeltaJ# is the change in the total angular momentum.

It is valuable to recognize the choice rules if you want to predict exactly how an excited state configuration can be written just based on the atom\"s (correct) ground state configuration.

EXAMPLES OF electronic EXCITATION TRANSITIONS

Allowed:

An example of an allowed electronic transition upwards the one unpaired electron to an empty 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# due to the fact that the electron didn\"t obtain paired through any brand-new electron. It began out unpaired, and also it remained unpaired (#m_s^\"new\" = m_s^\"old\"#), therefore #DeltaS = m_s^\"new\" - m_s^\"old\" = 0#.

Forbidden:

An instance of a forbidden electronic transition upwards of 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# since for #s#, #l = 0#, and for #d#, #l = 2#. Thus, #DeltaL = +2#, i m sorry is bigger than is allowed, so the is forbidden.

#DeltaS# is still #0# due to the fact that it\"s the exact same electron transitioning together before, simply towards a various orbital.

TERM icons / CONTEXT

\"I\"ve never ever seen #L#, #S#, or #J# before. Huh? What space they used for?\"

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DISCLAIMER: The above link describes term signs for context. It helps to recognize this, yet you don\"t need to know this like the ago of her hand uneven you are taking physical Chemistry.

APPLICATION the THE selection RULES

Alright, for this reason let\"s use the choice rules themselves. I gave examples already, therefore let\"s job-related off of the allowed shift example and adjust it a small bit. The values for #L#, #S#, and #J# are pretty similar.

Let us study this energy level diagram because that sodium:

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You have the right to see currently on the diagram going from the #3s# orbit to two #3p# orbital destinations. That shows either one excitation native the #3s# come the #3p# or a relaxation indigenous the #3p# to the #3s#.

These 2 lines are significant #589.6# and #589.0#, respectively, in #\"nm\"#, so what you check out happening is that sodium makes its #\"589 nm\"# excitation change (upwards), and then relaxes (downwards) to emit yellow light.

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Therefore, a common excitation/relaxation shift sodium provides 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 sodium is:

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

And the first excited state electron construction for sodium is:

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

Lastly, one easy means to mental what transitions are permitted is to keep in mind that electronic transitions on energy level diagrams are diagonal, and involves nearby columns.