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TuesdayOctober 23, 2012
(Valence Electrons and Electron Dot
Notation)
Bell Ringer Tuesday, 10-23-12
How many valence electrons does an atom need to have a stable
configuration?
What are the only elements that naturally have a stable electron
configuration?
How do atoms get a stable electron configuration if they do
not naturally have one?
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?
2 for H, He8 for all others
the Noble gases
by chemical bonding
sodiumLose 1 Los2 Lose 3
Lose or gain 4,share
Gain 3 Ga Gain 1 nada
magnesium
aluminum
silicon
phosphoru
s
sulfur
chlorine
argonL 1 L 2 L 3 L/G
4G 3 G 2 G 1 nad
a
Bell RingerTuesday, 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 Final Day
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 10/22 11/2
WS – Valence Electrons and
Electron Configuration
F5 10/22 10/24 10/26
WS – Average Atomic Mass F6 10/22 10/24 10/26
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.
Valence Electrons
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.
Valence Electrons
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.
Valence Electrons
Number of Highest Energy Level
Electrons (Main Blocks Only)
12 3 4 5 6 7
8
Electron-Dot NotationThus far we have seen three different types
of notation:
isotopic notation
electron configuration notation
orbital notation1s2, 2s2, 2p2
_____ _____ _____ _____ _____ 1s 2s 2px 2py 2pz
Electron-Dot NotationHere’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 NotationExample: Carbon
Carbon is in group 14 and has four valence electrons.
1s2, 2s2, 2p2
Here’s carbon’s electron-dot notation:
C1. Start with the elemental symbol.2. In your mind, divide the symbol into
quadrants, like a tic-tac-toe grid.3. Beginning in any quadrant put a dot to
indicate a valence electron.4. Continue in a clock-wise direction,
putting one dot in each quadrant before any quadrant gets a second dot.
5. Stop when you have put in the number of dots that correspond to the number of valence electrons that element has.
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Electron-Dot NotationExample: Fluorine
Fluorine is in group 17 and has seven valence electrons.
1s2, 2s2, 2p5
Here’s fluorine’s electron-dot notation:
F1. Start with the elemental symbol.2. In your mind, divide the symbol into
quadrants, like a tic-tac-toe grid.3. Beginning in any quadrant put a dot to
indicate a valence electron.4. Continue in a clock-wise direction,
putting one dot in each quadrant before any quadrant gets a second dot.
5. Stop when you have put in the number of dots that correspond to the number of valence electrons that element has.
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Electron-Dot Notation
WorksheetElectron Dot Notation