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molecule
neutral group of atoms that are held together by covalent bonds
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molecular compound
a chemical compound whose simplest units are molecules
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chemical formula
indicates the relative numbers of atoms of each kind in a chemical compound by using atomic symbols and numerical subscripts
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molecular formula
shows the types and numbers of atoms combined in a single molecule of a molecular compound
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diatomic molecule
molecule containing only two atoms
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difference in electronegativities of two atoms for nonpolar-covalent bond
0.0-0.3
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difference in electronegativities of two atoms for polar-covalent bond
0.3-1.7 inclusive
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difference in electronegativities of two atoms for ionic bond
1.7-3.3
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bond energy
the energy required to break a chemical bond and form neutral isolated atoms
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octet rule
chemical compounds tend to form so that each atom, by gaining, losing, or sharing electrons, has an octet of electrons in its highest occupied energy level
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exceptions to the octet rule
Boron is stable with 6; Beryllium with 4; Family members below Sulfur are stable with 12 valence electrons, and those of phosphorus are stable with 10 valence electrons
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electron-dot notation
an electron-configuration notation in which only the valence electrons of an atom of a particular element are shown, indicated by dots placed around the element's symbol
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lewis structures
formulas in which atomic symbols represent electron pairs in covalent bonds, and dots adjacent to only one atomic symbol represent unshared electrons
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structural formula
indicates the kind, number, arrangment, and bonds, but not the unshared pairs of electrons; lewis structures without dots
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single bond
covalent bond in which one pair of electrons is shared between two atoms
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multiple bonds
more than 1 pair of electrons shared between two atoms
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resonance
bonding in molecules or ions that cannot be correctly represented by a single lewis structure
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resonance structure
system of lewis structures eg. O-O=O <----> O=O-O
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VSEPR
valence-shell, electron pair repulsion
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VSEPR theory
repulsion between the sets of valence electrons surrounding an atom causes these sets to be oriented as far apart as possible
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assumption of VSEPR theory
electrons in molecules repel each other
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geometry of AB3
trigonal-planar
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geometry of AB4
tetrahedral
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geometry of AB3E
trigonal pyrimidal
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geometry of AB2E2
angular
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geometry of AB5
trigonal bipyramidal
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geometry of AB6
octahedral
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hybridization
the mixing of two or more atomic orbitals of similar energies on the same atom to produce new hybrid atomic orbitals of equal energies
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example of hybridization
CH4; 2S and 2P orbitals combine to form SP3 orbitals
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hybrid orbitals
orbitals of equal energy produced by the combination of two or more orbitals on the same atom
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intermolecular forces
forces of attraction between molecules
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dipole
created by equal but opposite charges that are separated by a short distance
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dipole-dipole forces
forces of attraction between polar molecules
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determine molecular polarity
bond polarity and molecular geometry
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hydrogen bonding
intermolecular force in which a hydrogen atom that is bonded to a highly elecronegative atom is attracted to an unshared pair of electrons of an electronegative atom in a nearby molecule
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london dispersion forces
intermolecular attractions resulting from the constant motion of electrons and creation of instantaneous dipoles
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reason for low melting point of noble gases and nonpolar molecular compounds
london dispersion forces only attraction between abovementioned
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directly related to number of electrons
strength of london dispersion forces
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