Chemistry Reference
In-Depth Information
We write the
electronic configuration
by listing each subshell in order of
increasing energy, with a superscript giving the number of electrons in that sub-
shell. That is, the detailed electronic configuration for a neon atom is
Number of electrons in each subshell
1
s
2
2
s
2
2
p
6
Ne
Principal
Letter designation for subshell
quantum number
based on angular momentum quantum number
This configuration is read aloud as follows: “one ess two, two ess two, two pee
six.” (The superscripts are not exponents, so words such as
square
are not used.)
The sum of the superscripts is the total number of electrons in the atom.
EXAMPLE 4.13
Using sets of quantum numbers from Table 4.2, write the detailed electronic
configuration of fluorine.
Solution
Fluorine, with atomic number 9, has 9 electrons. The first 9 electrons shown in
the table will fit into three subshells, as follows:
1
s
2
2
s
2
2
p
5
Note that the 2
p
subshell can hold a maximum of 6 electrons, but in fluorine,
only 5 electrons are left for that subshell.
Practice Problem 4.13
What element has the following electronic
configuration?
1
s
2
2
s
2
2
p
3
EXAMPLE 4.14
Write the detailed electronic structure of vanadium (V). Comment on the rela-
tive energies of the “last” 5 electrons.
Solution
1
s
2
2
s
2
2
p
6
3
s
2
3
p
6
4
s
2
3
d
3
Because the “last” 3 electrons are added to an inner shell (following the
rule) instead of the outermost shell, the 3
d
subshell of a vanadium atom must
be higher in energy than the 4
s
subshell.
n
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