Periodic Table Shortcut
Noble Gas Notation
Lewis Dot Structures
When we write electron
configurations, do we
need to always start at the
beginning?
No, there are a few shortcuts.
The first shortcut involves the
placements of element’s on the
periodic table
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Let us look at the electron configurations from
yesterday’s homework and bell work from
today and see how they fall on the periodic
table.
You will need 4 color pencils for this.
So, the periodic table is
arranged with electron
configurations in mind
The only exception is He
The rows and columns
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The rows correspond to the principle
quantum number (n)
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In other words, each time you drop a row on the
periodic table, you go out an energy level.
Be careful with the d and f areas
The d area is n-1 and the f area is n-2
La and Ac are considered the first f area elements
The sets of columns correspond to l quantum
numbers and the amount of electrons in that
orbital
So, by looking at the
periodic table, one can
find an element’s
electron configuration
Let’s try some examples:
Remember it should be a number
then a letter then a superscript
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What is the last orbital of tin (Sn)?
What is the last orbital of Ruthenium (Ru)?
What is the last orbital of Holmium (Ho)?
What element ends with the electron
configuration of:
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5s1
6p4
5f3 (remember Ac is first f)
The second shortcut
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We need to find a group of elements that
have completed or full orbitals.
That group is the noble gases.
The last column on the periodic table.
This group can be used to write an
abbreviated version of an element’s electron
configuration.
Let’s look at yesterday’s
homework again
How to write Noble Gas
Notation
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Find the closest _________ noble gas to
the element in atomic number without
going over.
Write that noble gas’s symbol in brackets.
Go back to the beginning of the row and
work back to the elements writing down
the orbital sections and counting the
electrons as you go.
Examples
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As (Atomic Number – 33)
What is the closest Noble gas without going
over?
Ar
So, [Ar] 4s2 3d10 4p3
C
 [He]2s22p2
Pb
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[Xe] 6s2 4f14 5d10 6p2
Lewis Dot Formulas
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Shows the valence electrons of an atom
Valence electrons are the electrons in the
outermost energy level
The only electrons that are in the outermost
energy level are s and p.
Therefore, the most valence electrons an
atom can have is 8 (2 from the s and 6 from
the p).
Lewis Dot Formulas
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So, Lewis Dot Formulas are the chemical
symbol surrounded by dots.
There will be one dot per electron in the s
and p orbital
Hund’s rule must be followed
What is the Lewis Dot
Structure for the following?
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Francium
Arsenic
Hydrogen
Krypton
Oxygen