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Octet Rule Exceptions
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Incomplete Octet: elements that are stable with <8 electrons in valence shell. Hydrogen (stable w/ 2), helium (2), lithium (2), beryllium (4), & boron (6)
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Octet Rule Exceptions
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Expanded Octet: elements in period 3 or greater that can hold more than 8 valence electrons by placing them in the d orbitalPhosphorous (10), sulfur (12), chlorine (14), etc.
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Octet Rule Exceptions
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Odd Number of Electrons: molecules w/ odd # of valence electrons cannot distribute electrons so that each atom will have 8.Ex: nitric oxide has 11 valence electrons, uneven distribution
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Ionic Bond
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Electrons are not actually shared, but an electron is transferred from atom w/ low ionization energy to element w/ high electron affinity. This makes one of them a cation & the other an anion, & causes them to be electrostatically attracted to each other. Form into a crystal lattice shape, where opposing forces are minimized.Difference in electronegativity (ΔEN) >1.7
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Ionic Compound Properties
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Dissociate in water & polar solvents, have high melting points due to the great attraction between the cation & anion.
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Covalent Bond
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When two atoms share electrons to form a double, single, or triple bond. Can be polar or nonpolar
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Bond Order
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Refers to whether a bond is single, double, or triple. As bond order increases, bond strength increases, & bond length decreases.
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Nonpolar bond
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Both atoms have exact same electronegativity. Bonds are nonpolar if their ΔEN (difference in electronegativity) is < 0.5
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Polar Bonds
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Atoms have significant difference in electronegativity, ΔEN of 0.5 - 1.7, but not enough to transfer electrons & form an ionic bond.
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Coordinate Covalent Bonds
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Formed when single atom provides both bonding electrons & other atom doesn't give any. Most often found in Lewis acid-base chemistry
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Formal Charge Formula
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Formal Charge = V - Nnonbonding - 1/2(Nbonding) V = # of valence electrons the atom normally hasNnonbonding= # of valence electrons atom isn't using in bonds (lone pair electrons)Nbonding = # of valence electrons atom is using in bonds
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Resonance Structure
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Found in any molecule that has pi bonds, most stable are those w/ least amount of formal charges. Actual structure of molecule is a combination of all resonance structures.
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Electronic Geometry (VSEPR Theory)
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The position of all electrons in a molecule, whether bonding or nonbonding
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Molecular Geometry (VSEPR Theory)
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The position of only the bonding pairs of electrons in a molecule
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Polarity of nonpolar molecules
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Nonpolar molecules may contain nonpolar bonds, or polar bonds whose dipole moments cancel each other out (must look at molecular geometry of a molecule to check)
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