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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 .
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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 • Combining of the dot diagrams to show bonding and to predict shape.
Steps for Lewis Structures • Add up total number of valence electrons. • 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. • Distribute the electrons as PAIRS. Start from the outside and move inward. • 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 • SO42- • NH4+ • CO32-
Review Draw the Lewis structures for: • CO2 • F2 • CH2Cl2 • SO32-
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 • TrigonalPyrimidal • NO3- • Trigonal Planar • SO42- • Tetrahedral • SF2 • Bent • SiO2 • Linear