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the behavior of an atom is most determined by
its electron configuration
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the behavior of a molecule is most determined by
the molecule's shape
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how do you determine a molecule's shape?
look at the distribution of electrons in the molecule, using a Lewis dot diagram
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for all atoms that form covalent bonds, the outermost energy level must
have a total of 8 electrons
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Which covalently bonded electrons don't have 8 electrons in the outermost level?
- hydrogen
- lithium
- beryllium
- boron
- groups 1, 2, & 13
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lone pairs
unshared pairs of electrons
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double bonds
share 2 electron pairs
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each bond of shared electrons and each pair of unshared electrons in the outermost energy level form a
- charge cloud
- repels other charge clouds
- this is the electrostatic repulsion of 2 or more negative charges
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what determines the arrangement of orbitals?
electrostatic & Pauli exclusions
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orbital arrangement determines
molecular shape
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why do electron pairs spread apart as far as possible in a molecule to
minimize repulsion forces
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shape 1
- if there are 2 pairs of shared electrons around a central atom, the shared pairs will be on opposite sides of the central atom
- Linear molecule
- the angle between the shared pairs is 180
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shape 2
- if there are 3 pairs of shared electrons around a central atom, a trigonal planar molecule is formed
- the angle between the pairs is 120
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shape 3
- if there are 4 pairs of shared electrons around a central atom, a tetrahedral molecule is formed
- angle is 109.5
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shapes 1, 2, and 3 have
no unshared pairs of electrons
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the repulsion between unshared pairs of electrons is
stronger than the repulsion between shared pairs
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shape 4
- if there are 3 shared and 1 unshared pair of electrons around a central atom, a pyramidal molecule is formed
- angle is 107
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shape 5
- if there are 2 shared and 2 unshared pairs of electrons, an angular or bent molecule is formed.
- angle is 104.5
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shape 6
- if the molecule is closed, a cyclic molecule is formed
- a ring- closed
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molecules ehich contain atoms bonded by polar covalent bonds will also be polar, unless
the molecules have symmetry, which makes the molecule non-polar
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hybrid orbitals
form when s & p orbitals overlap in a covalent bond
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sigma bond
when 2 hybrid orbitals from 2 different atoms form a bond by overlapping directly on a bond axis
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pi bond
when 2 hybrid obitals from 2 different atoms bond by overlapping sideways, a pi bond is formed
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a sigma bond forms a
single bond
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a sigma bond and a pi bond form a
double bond
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a sigma bond and 2 pi bonds form a
triple bond
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a double bond is a
sigma & pi
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a triple bond is a
sigma & 2 pi
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what makes benzene (C6H6) very stable?
overlapping of pi bonds cause the electrons to be shared all around the ring- these are delocalized pi electrons
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conjugated system
when multiple pi orbitls overlap
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catenation
the ability of all carbon atoms to form chains of varying lenghts
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simple hydrocarbons
- use a stem & -ane
- contain only single bonds
- saturated compounds
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double bonded hydrocarbons
same stem, add -ene
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triple bonded hydrocarbons
same stem, add -yne
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isomers
2 or more compounds which have the same molecular formula but have different structural formulas
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structural isomers
differ only in the position of the carbon atoms in relation to each other
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positional isomers
differ only in the relative position of a double or triple bond between carbon atoms
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functional isomers
- contain atoms besides carbon and hydrogen
- named based on the position of their new atoms
- the new atoms form "functional groups"
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functional groups
- ex: The alcohol group- OH
- when organic compounds contain an alcohol groupd, they end in -ol
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geometric isomers
composed of the same atoms bonded in the same order but with different order around a double bond
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cis
on the same side as the double bond
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trans
on the opposite side of the double bond
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