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Lewis Structures . Lewis Dot Diagrams . Show the valence electrons for an element. Steps. Draw element Symbol Place the number of electrons around the symbol. One dot per electron. Ex. Carbon . Examples . Silicon Oxygen Fluorine . Lewis Structures . - PowerPoint PPT Presentation
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LEWIS STRUCTURES
Lewis Dot Diagrams Show the valence electrons for an
element. Steps.1. Draw element Symbol2. Place the number of electrons around
the symbol. One dot per electron. Ex. Carbon
Examples Silicon
Oxygen
Fluorine
Lewis Structures Combining of the dot diagrams to show
bonding and to predict shape.
Steps for Lewis Structures 1. Add up total number of valence electrons.2. Draw a skeleton (Carbon, the solo element,
or the most electronegative element goes in the middle)★Hydrogen and the Halogens CANNOT be in the center.
3. Distribute the electrons as PAIRS. Start from the outside and move inward.
4. Count and adjust electrons till each element has 8. (except Hydrogen)
Examples CF4
PH3
H2O
O2(Careful)
Polyatomics Same as compounds but you must
add/subtract the charge from the electrons in step 1.
And place the structure in brackets with the charge outside.
Ex. Hydroxide. How many electrons in a neutral OH?7 How many in OH-?8
Examples SO4
2-
NH4+
CO32-
Review Draw the Lewis structures for:
CO2
F2
CH2Cl2
SO32-
VSEPR THEORY (A FANCY WAY TO PREDICT SHAPES)
VSEPR Stands for “Valence shell Electron pair
Repulsion” V-Valence S-Shell E-Electron P-Pair R-Repulsion Basically Electrons don’t like each other
very much!
5 Shapes Tetrahedral- four single bonds Trigonal Pyramidal- 3 single bonds and 1
lone pair Trigonal planar – 2 single, 1 double Bent- 2 bonds (any type) and lone pairs Linear- 2 bonds no lone pairs or just 2
atoms
PracticeDraw the Lewis structure and predict the shape
CF4 Tetrahedral
PH3 Trigonal Pyramidal
SO3 Trigonal Planar
H2O Bent
Predict the shape of the following PF3
Trigonal Pyrimidal
NO3-
Trigonal Planar
SO42-
Tetrahedral
SF2 Bent
SiO2 Linear
LAB TIME!
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