Chemistry Reference
In-Depth Information
neon, with 8 valence electrons, is a more stable state for the magnesium
atom to be in. Pieces of the puzzle continue to fall into place.
Up to this point, we have been discussing the “ground state” or normal
state of the various elements for which we did the electron configuration.
When an electron gains additional energy (from a source of heat, light, elec-
tricity, and so forth), it can temporarily move up to a higher energy level.
This “excited state” is unstable, and the electron quickly releases the addi-
tional energy in the form of visible light and falls back to its ground state.
Most instructors will want their students to be able to recognize the electron
configuration of an atom in this excited state. You probably won't be asked
to write the electron configuration of an atom in the excited state, because
you wouldn't know which electron moves up to a higher energy level, but
you should be able to recognize when a configuration for an excited state is
being shown.
Comparing the Ground State Configuration
to the Excited State
Excited State
Configuration
1s
2
2s
2
2p
4
3s
1
1s
2
2s
2
2p
5
3s
1
1s
2
2s
2
2p
6
3p
1
Look at some ex-
amples of the normal
(ground state) electron
configurations, and com-
pare them to their con-
figurations in examples
of excited state.
Can you recognize
the “look” of an atom in
the excited state? In each
Ground State
Configuration
1s
2
2s
2
2p
5
1s
2
2s
2
2p
6
1s
2
2s
2
2p
6
3s
1
Element
Fluorine
Neon
Sodium
Figure 3-4f
case, one or more electron has been “promoted” to a higher energy level.
For example, when the “3s
1
” electron in the sodium atom gets excited, it
jumps up to the “3p
1
” position. Take note of the fact that the atomic num-
ber, which we determine by adding all of the exponents, does not change.
We still have the same number of electrons in the excited state.
Let's review some questions from this somewhat difficult, yet impor-
tant, lesson. Be sure to check your answers at the end of the chapter.
Lesson 3-4 Review
1.
How many sublevels does the second energy level contain?
2.
How many orbitals does a “p” sublevel contain?
3.
How many total electrons can the fourth energy level hold?
4.
How many electrons can an “f” orbital hold?
