Tuesday
October 23, 2012
(Valence Electrons
and Electron Dot
Notation)
Tuesday, 10-23-12
How many valence electrons does an atom need to have a stable
configuration?
2 for H, He
8 for all others
What are the only elements that naturally have a stable electron
configuration?
the Noble gases
How do atoms get a stable electron configuration if they do not
naturally have one?
by chemical
bonding
Most atoms have stable electron configurations if they have eight
valence electrons (called a stable octet.) What would the following
atoms have to do in order to get these eight valence electrons?
sodium magnesium aluminum Lose
siliconor phosphorus sulfur chlorine argon
Lose
Los2
Lose
Gain
nada
gain4 4,
L1 1
L2
L 3 3 L/G
G3 3
GGa2 Gain
G 1 1 nada
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Tuesday, 10-23-12
Write the electron configuration
notation for the following atoms:
H, He, Li, C, O, Ne, Na, Cl
Announcements
Assignment Currently
Open
Summative or
Formative?
Date Issued
Date Due
Date Into
GradeSpeed
QUIZ 6
S3
10/5
10/5
10/26
QUIZ 7
S4
10/12
10/12
10/26
Pop Quiz – The
Periodic Table and
the Periodic Law
F4
10/16
10/16
QUIZ 8
S5
10/19
10/19
WS – Valence
Electrons and
Electron
Configuration
F5
10/22
10/24
10/26
WS – Average
Atomic Mass
F6
10/22
10/24
10/26
10/22
Final Day
11/2
The element chlorine has
an electron configuration
notation of:
1s2, 2s2, 2p6, 3s2, 3p5
Chlorine has 7 electrons in
its highest energy level (3),
2 in the s sub-level and 5
more in the p sub-level.
Chlorine counts all 7 of
these valence electrons in
its bonding considerations.
For main block (s and p) elements,
the valence electrons are the
electrons in the outermost s- and
p- sublevels.
The inner electrons are in filled
energy levels and are held too
tightly by the nucleus to be
involved in compound formation.
The alkali metals of group 1 have 1
valence electron.
The alkaline earth metals of group 2 have
2 valence electrons.
The elements in the p block (groups 13–
18) have a number of valence electrons
equal to their group number minus 10.
For example, group 13 has 3 valence
electrons, group 14 has 4, etc.
In some cases, both the s- and p- sublevel
valence electrons of the p-block elements
are involved in compound formation.
In other cases, only the electrons from the
p-sublevel are involved.
1
2
Number of Highest
Energy Level
Electrons (Main
Blocks Only)
8
3 4 5 6 7
Electron-Dot Notation
Thus far we have seen three different types
of notation:
isotopic notation
electron configuration notation
1s2, 2s2, 2p2
orbital notation
_____ _____ _____ _____ _____
1s
2s
2px 2py 2pz
Electron-Dot Notation
Here’s a fourth type of notation:
Electron-Dot Notation is an
electron-configuration notation
in which only the valence
electrons of an atom are shown,
indicated by dots placed around
the element’s symbol.
Lower energy level, inner - shell
electrons are not shown.
Electron-Dot Notation
Example: Carbon
2
2
2
1s , 2s , 2p
Carbon is in group 14 and has four valence electrons.
Here’s carbon’s electron-dot notation:
¢
1.
2.
C
¢
¢
¢
3.
4.
5.
Start with the elemental symbol.
In your mind, divide the symbol into
quadrants, like a tic-tac-toe grid.
Beginning in any quadrant put a dot to
indicate a valence electron.
Continue in a clock-wise direction,
putting one dot in each quadrant before
any quadrant gets a second dot.
Stop when you have put in the number
of dots that correspond to the number
of valence electrons that element has.
Electron-Dot Notation
Example: Fluorine
2
2
5
1s , 2s , 2p
Fluorine is in group 17 and has seven valence electrons.
Here’s fluorine’s electron-dot notation:
¢
¢
¢
F
¢¢
1.
2.
¢
¢
3.
4.
5.
Start with the elemental symbol.
In your mind, divide the symbol into
quadrants, like a tic-tac-toe grid.
Beginning in any quadrant put a dot to
indicate a valence electron.
Continue in a clock-wise direction,
putting one dot in each quadrant before
any quadrant gets a second dot.
Stop when you have put in the number
of dots that correspond to the number
of valence electrons that element has.
Electron-Dot Notation
Worksheet
Electron Dot Notation