# Chapter 1B lecture Notes .ppt - Chapter 1 Lecture Notes 1B...

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Chapter 1 Lecture Notes 1B
Atoms with one, two, three, or four valence electrons form one, two, three, or four bonds, respectively, in neutral molecules. Atoms with five or more valence electrons form enough bonds to give an octet. In this case, the predicted number of bonds = 8 − the number of valence electrons. Lewis dots show the outermost central level of energy containing valence electrons Electron sharing (covalent bonding) is the glue that holds atoms together to form molecules . Covalent Bonding Covalent Bonding Patterns (1.2) Patterns (1.2)
1. Draw only the valence electrons. 2. Give every second-row element no more than eight electrons. 3. Give each hydrogen two electrons. Lewis structures are electron dot representations for molecules Lewis Structures Lewis Structures (1.3) hat if we have Magnesium fluoride?
Valence electrons Valence electrons
STEP 1: Arrange atoms next to each other that you think are bonded together Always place hydrogen atoms and halogen atoms on the periphery because H and X (X = F, Cl, Br, and I) form only one bond each. As a first approximation, use the covalent bonding patterns to help, remember: How To Draw a Lewis Structure How To Draw a Lewis Structure Example: Methylamine
Methanol, a compound with molecular formula CH 4 O, CH 3 OH Place the second-row elements, C and O, in the middle. Place three H's around C to surround C by four atom Place one H next to O to surround O by two atoms. STEP 2: Count the electrons Count the number of valence electrons from all atoms. Add one electron for each negative charge. Subtract one electron for each positive charge. This sum gives the total number of electrons that must be used in drawing the Lewis structure. STEP 3: Add the bonds and lone pairs Add the C-H, C-O, and O-H bonds, using 10 of the 14 electrons.
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