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Definitions |
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chlorine
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Cl2
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ethene
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C2H4
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fluorine
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F2
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methane
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CH4
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phosphane
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PH3
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ozone
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O3
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nitrogen
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N2
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sulfur trioxide
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SO3
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hydrogen peroxide
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H2O2
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hydrogen chloride
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HCl
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carbon monoxide
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CO
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VSEPR theory
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valence-shell electron-pair repulsion theory; because electron pairs repel, molecules adjust their shapes so that valence-electron pairs are as far apart as possible
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hydrogen bond
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a relatively strong intermolecular force in which a hydrogen atom that is covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of another electronegative atom in the same molecule or one nearby
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molecular orbitals
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an orbital resulting from the overlapping of atomic orbitals when two atoms combine
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dispersion force
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the weakest find of intermolecular attraction; this attraction is thought to be caused by the motion of elections
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3 0 3
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Trigonal Planar/ Trigonal Planar/ 120/ sp2/ Ex: AlCl3, SO3
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4 0 4
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Tetrahedral/ Tetrahedral/ 109.5/ sp3/ Ex: CH4
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bonding orbital
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a molecular orbital whose energy is lower than that of the atomic orbitals from which it is formed
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unshared pairs
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pairs of valence electrons that are not shared between atoms; aka lone pairs or nonbonding pairs
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sp2-hybridized orbital
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Central atom singly or doubly bonded to three other atoms is sp2-hybridized. Trigonal planar.
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2 0 2
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Linear/ Linear/ 180/ sp/ Ex: BeCl2
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Step 1 to VSEPR Theory
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1. Draw Lewis Structure
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polar bond
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a bond formed when two different atoms are joined by a covalent bond and the bonding electrons are shared unequally
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polar molecule
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a molecule, like water, in which one or more atoms is slightly negative and one or more is slightly positive, unless molecular geometry causes the polarities to cancel each other out
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tetrahedral angle
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a bond angle of 109.5 degrees created when a central atom forms four bonds directed toward the corners of a regular tetrahedron
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Sigma orbitals and bonds
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Are cylyndrical around the axis joining the two nuclei and result from the overlap of two s-orbitals, two p-orbitals, or an s and a p-orbital, or the overlap of other hybrid orbitals.
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Bond length comparison
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propane, C-H 110 pm, C-C 153 pm
propene, C-H 108 pm, C=C 134 pm
propyne, C-H 106 pm, carbon-carbon triple bond 121 pm
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Average bond energy and ΔrH
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Determined experimentally by measuring the average covalent bond energies for a variety of typical molecules. Useful for estimating enthalpy changes in reactions.
CH2=CH2 + H-H ==> CH3-CH3, ΔrH = -31
Bonds broken:
C=C, +146kcal/mol
H-H, +104kcal/mol
Bonds formed:
C-C, -83 kcal/mol
2 x C-H, -99 kcal/mol
Total enthalpy of reaction, ΔrHo = -31, which means it's exothermic because it gives off more energy than it consumes.
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1 2 3
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Trigonal Planar/ Paired/ N/A / sp2/ Ex: O2
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double covalent bonds
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bonds that involve two shared pairs of electrons
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1 1 2
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Linear/ Paired/ N/A / sp/ Ex: CO, N2
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nonpolar covalent bond
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a bond formed when the atoms in a molecule are alike and the bonding electrons are shared equally
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Step 2 to VSEPR Theory
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2. Count Electron pairs and arrange them to minimalize repulsion
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Step 4 to VSEPR Theory
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4. Determine the name of the molecular structure from how the atoms are arranged
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single covalent bond
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a bond in which two atoms share a pair of electrons
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Pi orbitals and bonds
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Have a nodal plane and result from the sideways overlap of two p-orbitals. sp2-hybridized carbon has an unhybridized p orbital, which can form a pi bond by overlapping side to side with a p orbital of an adjacent atom (C, N, or O) to which it is already joined by a sigma bond; the pi and sigma bond together constitutes a double bond. sp-hybridized carbon has two unhybridized p-orbitals and forms a triple bond with another C or N, made up of a sigma and two pi bonds.
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Rule 2 of the VSEPR Theory
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2. Three pairs of electrons are always 120 degrees apart (Trigonal Planar)
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Rule 1 of the VSEPR Theory
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1. Two pairs of electrons on central atom are always 180 degrees apart (Linear)
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Step 1 for Drawing Lewis Structure
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1. Add all valence electrons of all atoms.
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