SUMMERY (SUMMARY) OF ELECTRON
CONFIGURATIONS
THE GROUND STATE CONFIGURATION:
1) Given on periodic table.
2) Inner shells are full ( except transition metals, where the last two shells may be
incomplete).
3) Most stable, lowest energy configuration.
4) Lower shell numbers are closest to the nucleus and are lowest in energy level.
5) Electrons must exist in shells, also termed energy levels and principle
quantum number.
6) The outer shell is the valence shell and is chemically reactive, inner shells are
kernel electrons and are chemically inactive.
THERE ARE TWO
ELECTRONS IN
SHELL N=1 ( lowest
energy level in Na)
THERE ARE EIGHT
ELECTRONS IN
SHELL N=2
11Na
2-8-1
2-8-1
THERE IS ONE
ELECTRON IN SHELL
N=3 VALENCE
SHELL( highest
energy level here)
THERE ARE TWO
ELECTRONS IN
SHELL N=1
25Mn
2-8-13-2
THERE ARE TWO
ELECTRON IN SHELL
N=4 VALENCE SHELL
2-8-13-2
THERE ARE EIGHT
ELECTRONS IN
SHELL N=2
THERE ARE 13 ELECTRONS IN SHELL N=3,
TRANSITION METALS (GROUPS 3-12)
FREQUENTLY HAVE THE OUTER TWO SHELLS
INCOMPLETE.
THIS
BACKGROUND
IS CORN-Y
THE EXCITED STATE CONFIGURATION:
1) Same number of electrons as ground state, different configuration.
2) An electron is promoted from an inner shell (lower energy) to an outer shell
(higher energy).
3) An inner shell that is full in the ground state will be incomplete in the excited
state.
4) The excited state is temporary and is imediatley followed by fallback.
11Na
2-8-1
THIS INNER
SHELL IS NOT
FULL (SHOULD
HAVE 8
ELECTRONS)
WHICH IS
INDICATIVE OF AN
EXCITED STATE.
2-8-1
GROUND STATE
2-7-2
EXCITED STATE
1-8-2
EXCITED STATE
11Na
EXCITATION
eENERGY
ee-
2-8-1
e-
e-
e-
n=3
e-
e-
e-
n=2
e-
enuc
n=1
11Na
2-7-2
e-
EXCITED STATE, THE
ELECTRON IS IN A HIGHER
ENERGY LEVEL THAN ITS
GROUD STATE POSITION.
e-
ee-
e-
n=2
e-
ee-
ELECTRON HOLE, THE
VACATED FORMER POSITION
OF THE ELECTRON, THE n=2
SHELL IS NO LONGER
COMPLETE.
e-
n=3
e-
enuc
n=1
e-
2-7-2
DURING FALLBACK
ENERGY IS
RELEASED AS
LIGHT
e-
FALLBACK
11Na
DURING FALLBACK
ENERGY IS
RELEASED AS
LIGHT
e-
eee-
e-
n=3
ee-
DURING FALLBACK THE
ELECTRON BECOMES MORE
STABLE AS IT RELEASES ITS
ENERGY, GOES BACK TO
GROUND STATE.
e-
n=2
enuc
n=1
11Na
e-
2-8-1
e-
e-
e-
e-
ee-
ee-
n=2
e-
enuc
n=1
n=3
INCREASING ENERGY
U DO IT NOW!
For the following configuration: 2-8-18-6
a) Identify the element.
Simply add the electrons, which equal protons in a neutral atom,
the atomic number.
2-8-18-6: 2+8+18+6 = 34 electrons indicates an
atomic number of 34, which is Se
b) Propose an excited state.
Write a configuration with the same number of electrons as the
ground state , but with a different configuration.
2-8-18-6(ground): 2-8-17-7 (excited)
♫NOTE – electrons furthest from the nucleus are most likely to be excited
(promoted).
c) How many electrons are in the valence shell?
2-8-18-6, 6 valence electrons (and 2+8+18 = 26 kernel)