Test Four – Chemistry – Flashcards
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bonding lowers the |
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potential energy between positive and negative |
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Atomic Size - |
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related to the distance between atoms in a sample of the element |
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Transition Metals: |
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the trend in size changes slightly since electron/electron repulsions counteract the decrease in size as we go across a period |
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Ionization Energy - |
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The energy required to remove an electron from an atom in the gas phase |
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As atomic radius decreases, the ionization energy _____ |
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increases |
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Electron Affinity - |
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The energy change for a process in which an electron is acquired by the atom in the gas phase or “how bad an atom wants an electron.” |
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Isoelectronic Ions: |
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Ions that have the same number of electrons (but different number of protons). N-3, O-2, F-, Na+,and Mg+2 |
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Chemical Bond: |
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When a chemical reaction occurs between two atoms, their valence electrons are reorganized so that a net attractive force occurs between atoms. |
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Ionic bond: |
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forms when one of more valence electrons is transferred from one atom to another. Produces a positive and negative ion. The “bond” is the attraction between the ions |
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Covalent bond: forms by |
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the sharing of valence electrons between atoms. |
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Metal with nonmetal bonding – |
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electron transfer and ionic bonding |
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Covalent bonding – |
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occurs most commonly between non mental atoms |
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Metal with metal bonding – |
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electron pooling and metallic bonding |
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Metallic bonding – |
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metal atoms sharing valence electrons but not by covalent bonding |
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Octet rule – |
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when atoms bind, they lose, gain, or share electrons to attain a filled outer level of eight electrons or two for H and Li |
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The lattice energy |
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the enthalpy change that occurs when 1 mol of ionic solid separates into gaseous ions |
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Ionic solids exist only because |
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the lattice energy exceeds the energy required for the electron transfer |
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Formation of a covalent bond always results in |
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a greater electron density between the nuclei |
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Bond order – |
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the number of electron pairs being shared by a given pair of atoms |
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Single bond – |
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the most common band and consists of one bonding pair of electrons |
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Double bond – |
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consists of two bonding pairs of electrons, four electrons shared between two atoms so the bond order is 2 |
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Bond energy – |
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the energy needed to overcome this attraction and is defined as the standard enthalpy change for breaking the bond in 1 mol of gaseous molecules |
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Bond length – |
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the distance between the nuclei of the two bonded atoms |
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Bond order to directly related to _____and inversely related to ______ |
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bond energy; bond length |
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Most covalent substances have low electrical conductivity because |
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their electrons are localized and ions are absent |
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Electronegativity – |
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the relative ability of a bonded atom to attract shared electrons |
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An important use for electronegativity is |
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determining an atom’s oxidation number |
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When atoms of different electro negativities form a bond, the bonding pair is shared ____ |
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unequally |
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Polar covalent bond – |
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unequal distribution of electron density |
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Electronegativity difference - |
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the difference between the electronegativity values of the bonded atoms |
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Electronegativity difference is directly related to a bond’s _____ |
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polarity |
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As the ?EN decreases, the bond becomes more ____ |
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covalent |
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Bond Dissociation Enthalpy: |
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the enthalpy change for breaking a bond in a molecule with the reactants and products in the gas phase |
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Polar Bond: |
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When the bond between two atoms has a positive and negative end or pole. |
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Hydrogen atoms from ____ bonds |
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one |
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Carbon atoms from _____ bonds |
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four |
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Nitrogen atoms form _____ bonds |
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three |
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Oxygen atoms form ______ bonds |
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four |
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Fluorine is always a ______ |
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surrounding atom |
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Resonance structures – |
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have the same relative placement of atoms but different locations of bonding and lone pairs |
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Resonance hybrid – |
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average of the resonance forms |
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Partial bonding in resonance hybrid, often leads to ______ |
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fractional bond orders |
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Formal charge – |
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change an atom would have if the bonding electrons were shared equally |
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Electron deficient – |
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have fewer than eight electrons around the central nucleus |
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Free radicals – |
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species that contain a lone (unpaired) electron, which makes them paramagnetic and extremely reactive |
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Expanded valence shells occur only with _______ because they have d orbital available |
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nonmetals form period 3 or higher |
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VESPR Theory – |
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to minimize repulsions, each group of valence electrons around a central atom is located as far as possible from the others |
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Molecular shape – |
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three dimensional arrangement of nuclei joined by the bonding groups |
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The electron group arrangement is defined by |
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the bonding and nonbonding electron group |
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The Molecular shape is defined by |
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the relative positions of the nuclei, which are connected by the bonding groups only |
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Bond angle – |
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angle formed by the nuclei of the two surrounding atoms with the nucleus of the central atom at the vortex |
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Linear shape – |
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AX2 108o |
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Trigonal Planar– |
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AX3 120o |
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Tetrahedral – |
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AX4 109.5o |
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Trigonal Bipyramidal – |
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AX5 90o & 120o |
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Octahedral – |
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AX6 90o |
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Lewis electron dot symbols: developed by |
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Gilbert Newton Lewis |
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Bond pair: |
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The e- involved in the covalent bond. |
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Lone pair: |
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The e- not involved in bonding also called nonbonding e-. |
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Octet Rule: |
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The tendency of molecules and polyatomic ions to have structures in which eight e- surround each atom |
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Valence shell electron-pair repulsion is a method for |
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predicting the shapes of covalent molecules and ions. |
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Electron-pair geometry: |
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the geometry taken up by ALL the valence e- pairs around a central atom |
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Molecular geometry describes |
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the arrangement in space of the central atom and the atoms directly attached to it. |
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Valence Bond Theory created by |
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Linus Pauling |
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Bonding between the two atoms occurs when |
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the e- clouds on the two atoms interpenetrate or overlap |
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Orbital overlap increases the probability of |
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finding bonding e- in this region of space. |
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The idea that bonds are formed by overlap of atomic orbitals is the basis for |
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valence bond theory. |
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The covalent bond that arises from the overlap of the two s orbitals (1 from each H) is called |
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a sigma bond. |
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Liquids and solids resist |
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compression |
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Dipole-Dipole Attraction: |
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when one polar molecule encounters another, the positive end of one is attracted to the negative of the other, and via versa. |
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Hydrogen Bond: |
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The strong attraction between an electronegative atom with a lone pair and the hydrogen atom of the N--H, O--H, or F--H bond. |
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Dipole/Induced Dipole Forces: |
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polar molecules can induce a dipole in a molecules that do not have a permanent dipole. |
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As the water molecule approaches the O2 molecule a dipole is induced, this is referred to as _____ |
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polarization. |
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The degree to which the e- cloud distorts is called ______ |
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polarizability. |
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The larger the molar mass the greater the _____ |
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polarizability of the molecule. |
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Dipole/Induced Dipole Forces are weaker than _____ |
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electrostatic or dipole/dipole interactions. |
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Induced Dipole/Induced Dipole Forces are often referred to as _______ |
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London dispersion forces |
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London forces arise between |
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all molecules both polar and non-polar |
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London dispersion forces are the only intermolecular forces that |
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allow non-polar molecules to interact |
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Vaporization: |
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or evaporation is the process in which a substance in the liquid phase becomes a gas |
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The standard molar enthalpy of vaporization, ?vapHo (kJ/mol): |
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the energy required to vaporize a sample. |
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Condensation: |
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when a molecule loses efficient energy to reenter the liquid phase. (exothermic) |
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Equilibrium Vapor Pressure: |
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the pressure exerted by the vapor in equilibrium with the liquid phase. |
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The tendency of its molecules to escape from the liquid phase and enter the vapor phase, referred to as _______ |
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volatility. |
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Critical Point: |
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when a specific temp and pressure are reached, the interface between the liquid and the vapor disappears. |
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Critical Temperature: |
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the temperature at which this phenomenon is observed, and the corresponding pressure, critical pressure |
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Viscosity: |
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the resistance of liquids to flow |
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Surface Tension: |
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the energy required to break through the surface or to disrupt a liquid drop and spread the material out as a film. |