Transcript The groups, and electron dot diagrams

Electron
Configurations
- part III
- Short hand notation
- Valence electrons
Essential questions
Is there a way to write electron
configuration even easier?
 I’ve heard the valence electrons are the
important – what are they and why?

Valence Electrons
 Valence
electrons are the electron’s
located in the highest energy level
 These are the electrons that
determine the chemical properties of
an element
 And these are the electrons involved
in chemical reactions and bonding!
Valence Electrons
 Valence
electrons = electrons in ALL
the subshells with the highest
principal energy shell (outermost
shell)
 Core electrons = in lower energy
shells
 Atoms will try to either gain or lose
electrons in order to get to a full or
empty outer most shell
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Shorthand Notation
 A way
of abbreviating long electron
configurations
 Since we are only concerned about
the outermost or valence electrons,
we can skip to the closest noble gas
and then finish the configuration
The Noble Gas
Electron Configuration

The noble gases have 8 valence
electrons
 except

Noble gases are especially unreactive
 He

for He, which has only 2 electrons
and Ne are practically inert
Reason noble gases are unreactive is
that the electron configuration of the
noble gases is especially stable
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Shorthand Notation




Step 1: It’s the Showcase Showdown!
Find the closest noble gas to the atom (or ion),
WITHOUT GOING OVER the number of
electrons in the atom (or ion). Write the noble
gas in brackets [ ].
Step 2: Find where to resume by finding the next
energy level
Step 3: Resume the configuration until it’s
finished.
Step 4: Check by counting the total number of
electrons!
Shorthand Notation
 Let’s
try chlorine
Step 1
Step 2
Step 3
Step 4
Energy Levels
n=1
n=2
n=3
n=4
Let’s Practice
Work with a partner to write the electron
configurations for the first 20 elements on
your blank periodic table.
 The first 2 has been done for you
 You can use the noble gas notation for
elements after Neon

Electron Configurations and
the Periodic Table
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Take aways for shorthand
Electron configurations
1.
2.
The number of protons equals the atomic
number which equals number of
electrons
The number of the highest energy level
occupied by electrons equals the period
number of the element.
Take aways for shorthand
Electron configurations
3. The number of electrons in the highest
used energy level (valence level) equals
the roman numeral group number.
4. We can break up the periodic table in
blocks that correspond to the ending
configuration orbitals.
Orbitals and the Periodic
Table

Orbitals grouped in s, p, d, and f orbitals
s orbitals
d orbitals
p orbitals
f orbitals
What about valence electrons for
transition metals?
The general method for counting valence
electrons is generally not useful for the dblock transition metals.
 Therefore, we will focus on s and p block
elements.

Valence Electrons

Go back and write the number of valence
electrons for each of first 20 elements you
wrote the configuration for in the upper left
corner of the box and circle it.
Li
Ions
Can you predict if the atoms will want to
gain or lose electrons for fail to react
chemically?
 All atoms want to have full outermost
energy levels
 Go back and write the ion most likely to
form in the upper right corner of each box.
 See any trends?

Check for understanding
How many valence electrons does each
atom have?
carbon: 1s22s22p2 = 4
magnesium: 1s22s22p63s2 = 2
chlorine: 1s22s22p63s23p5 = 7
gallium: 1s22s22p63s23p6 4s2d104p1 = 3
Practice more

Let’s COMPLETE WORKSHEET 5-6
together
Electron Dot
Notation
Electron Dot Diagrams
• If you want to see how atoms of one
element will react, it is handy to have an
easier way to represent the atoms and
the electrons in their outer energy levels.
• An electric dot diagram is the symbol
for the element surrounded by as many
dots as there are valence electrons.
• # of dots = # of valence electrons
G.N. Lewis
Also known as Lewis Dot Structures
 Named after G.N. Lewis, an American
chemist who developed the method while
teaching chemistry class in 1902.

How to write them
N
• Start by writing one dot to the right of the
element symbol, then work your way
around clockwise adding dots to the
bottom, left, and top.
• Add a fifth dot to the right to make a pair.
Continue in this manner until you reach
eight dots to complete the level.
Check for understanding
1. Electrons are now known to swarm around
the nucleus of an atom in a configuration
known as the _______.
A. electron circle
B. electron cloud
C. electron configuration
D. electron swarm
The answer is B. The “cloud” includes all the
regions where an electron might be found.
Question 2
What information can you learn from this
diagram?
It tells you that nitrogen contains five electrons
in its outer energy level.
Question 3
The _______ an energy level is from the
nucleus, the ______ electrons it can hold.
A. closer, more
B. closer, less
C. farther, less
D. farther, more
The answer is D. The farthest shells contain the
greatest number of electrons.
Question 4
a. Write the shorthand electron configuration for
arsenic (atomic number 33)
b. What block is it in?
c. How many valence electrons does it have?
d. Write the electron dot diagram.
Question 4
a.
b.
c.
d.
[Ar] 4s2 3d10 4p3
p-block
3 valence electrons
Work on your own

Write the electron dot diagrams for the first
20 elements on the periodic table in your
packets.
Jeopardy Review Game

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