Using the periodic
table
chapter 4 & 11
The Periodic Table
Arrangement
The periodic table is arranged by orbital
diagrams.
Schrodinger gave us equations that
describe atomic orbitals. The values we
get from those equations are quantum
numbers.
We used quantum numbers to build
orbital diagrams, we used orbital
diagrams to build the periodic table
Using the periodic table to
determine orbital diagrams
The period relates to the energy level of
electrons
Therefore H and He only have electrons
in the 1st energy level
Li, Be, B, C ,N ,O ,F and Ne have
electrons up to the 2nd energy level
You can determine the
orbital by the placement
H
For these elements the last
electron is in the s orbital
He
Li
For these elements the last
electron is in the d orbital
for these elements
the last electron is
in the p orbital
For the elements the last electron
is in the f orbital
Determining the number
of electrons in the last
energy level
count the number of elements to the left
edge of the “section”
For example Al
It is the first element in the 2nd row of p
filling elements
The last electron for aluminum will be
the first electron possible in the 2nd p
Continuing…
Al
The last electron will be the first
possible in the 2nd p
•1 s __
•2 s __ p __ __ __
•3 s __ p __ __ __ d __ __ __ __ __
Condensed electron
configuration
long electron configurations are not normally
written out because it gets rather repetitive
Instead it is condensed, by starting from the
previous Noble gas and adding shells to it.
For example K
[Ar]4s1
This is the same as saying everything that is
in Ar (1s22s2p63s2p6) +4s1
Zr
[Kr]5s24d2
-> [Kr] 4d25s2
To Determine the
Condensed electron
configuration
Start at the previous noble gas (lower
atomic number)
Write out every element in order of
atomic number to your given
Determine which shell all elements are
filling. The number of elements in that
shell is your superscript number.
For Iron
Previous Noble Gas----Ar
Write all elements
K Ca Sc Ti V Cr Mn Fe
These fill 4 s
These fill 3 d
So it is
[Ar]3d64s2
Lone electron in the 5d
or 6 d
Odd exception
Lanthanum’s last electron fills the 5d orbital.
Ce has its last electron fill in the 4f, and the
one from 5d (La) jumps to 4f.
The next elements all fill up the 4f until
Gadolinium which fills up the 5d again.
A similar “jumping” of one electron occurs
with the actinide series
Different Periodic
Tables
The electron “jumping” is why there are
two forms of the periodic table in
common usage.
One has lanthanum and actinium in with
the d filling elements.
The other has lanthanum and actinium
with the f filling elements
Homework
For the following elements
Ignore the exception if you run into it.
fill in the last shell only of the orbital
diagram and do the condensed electron
configuration
Ti, Cl, Sr, Sn and O