Chemical Bonding - Terms

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*All page numbers are from Atkins, The Elements of Physical Chemistry, Second Edition
Term Page #* Definition/Explanation
antibonding orbital 345 An orbital, if occupied, decreases the strength of the bond between two atoms.
band gap 361 A range of energy where no band energies exist.
bond order(b) 352 For a diatomic molecule it is defined as the number of antibonding orbitals subtracted from the number of bonding orbitals.
bonding molecular orbital 343 A molecular orbital that contributes to the strength of the bond two atoms.
Born-Oppenheimer approximation 334 An assumption that the nuclei are so much heavier than the electrons that the nuclei can be treated as stationary with the electrons moving around them.
core orbitals 347 The orbitals of the inner, closed shell.
covalent bond 333 A chemical bond formed when two atoms share a pair of electrons.
delocalized 360 Each electron pair helps to bind several or all of the atoms together.
diamagnetic 353 A substance pushed out of a magnetic field because of paired electron spins in molecular orbitals.
dopants 363 Foreign atoms implanted in a semiconductor that can either withdraw electrons or donate electrons.
electronegative 355 The property of an atom to draw electrons towards itself.
equilibrium bond length 334 The distance between nuclei where the molecular potential energy curve is lowest. This is where the bond energy is least and the bond is therefore more stable.
even parity 354 When a molecule has been tested by inversion and the signs are the same.
Fermi level 362 Only truly defined at t=0, the Fermi level is the highest occupied molecular orbital.
heteronuclear diatomic molecule 355 A diatomic molecule formed from atoms of two different atoms.
highest occupied molecular orbital 358 The highest occupied molecular orbital.
homonuclear diatomic molecules 347 Diatomic molecules formed from identical atoms.
hybrid orbitals 38 Mixtures of atomic orbitals on the same atom.
hybridization 338 The blending together of the orbitals of an excited atom (one in which promotion has occurred).
insulators 360 Semiconductors that have a very low electrical conductivity.
inversion 354 The process of choosing a point outside a molecular orbital and noting the sign there, then passing through the center of the molecule to the opposite side and comparing the signs. If the signs are identical, it has even parity; if the signs are different, it has odd parity.
ionic bond 333 A chemical bond formed by the transfer of electrons from one atom to another and the consequent attraction between the ions formed.
ionic-covalent resonance 341 When the resonance of a molecule involves both ionic and molecular structures.
LCAO-MO 343 The term used to designate the approximate molecular orbital formed through linear combination of atomic orbitals.
linear combination of atomic orbitals 343 The simple addition of the two atomic orbitals to form the general shape of the corresponding molecular orbital.
lowest unoccupied molecular orbital 358 The lowest unoccupied molecular orbital.
metallic conductor 360 A substance in which conductivity decreases as the temperature increases.
molecular orbital energy level diagram 345 A chart displaying the relative energies of the atomic orbitals and the corresponding bonding and antibonding orbitals that they form.
molecular orbital theory 342 A theory in which electrons do not belong to particular bonds but rather that they should be treated a s spreading throughout the molecule.
molecular orbitals 342 An orbital similar to an atomic orbital, but which spreads over the entire molecule.
molecular potential energy curve 334 A graph of how the bond energy varies with internuclear distance.
nodal plane 344 A plane where the value of the wavefunction passes through zero.
nonpolar bond 357 A covalent bond in which the electrons are shared equally between the two atoms.
n-type semiconductor 363 A semiconductor where the dopants have a negative (hence the n) charge relative to the rest of the semiconductor.
odd parity 355 When a molecule has been tested by inversion and the signs are different.
overlap integral 349 overlap integral evaluated over all space to determine the extent to which two orbitals overlap.
p band 361 The band formed by the overlap of p orbitals.
paramagnetic 353 A substance drawn into a magnetic field because of unpaired electron spins in molecular orbitals.
parity 354 A molecule's symmetric property when tested under the process of inversion.
partial negative charge 356 When the electron pair in a bond is pulled closer to one atom, resulting in a net negative charge, denoted delta-.
pi bond 336, 348 A bond formed by the side-by-side pairing of electrons in p-orbitals
pi orbital 348 A molecular orbital that resembles a p orbital when viewed along the internuclear axis. More precisely, it is so called because an electron that occupies a pi orbital has one unit of orbital angular momentum around the internuclear axis, just as a p electron has one unit of orbital angular momentum around the nucleus.
polar bond 355 A covalent bond in which the electrons are not shared evenly.
polar covalent bond 357 A covalent bond in which the electrons are not shared equally between the two atoms, represented by the wavefunction polar covalent bond equation
promotion 338 The excitation of an electron to an orbital of higher energy.
p-type semiconductor 363 A semiconductor where the dopants have a positive (hence the p) charge relative to the rest of the semiconductor.
resonance 341 The superposition of different electron distributions in the same nuclear framework.
resonance hybrid 341 The hybrid formed by the superposition of the different resonance structures.
resonance stabilization 342 A resonance structure has a lower energy relative to the original structures because of the improvement of the wavefunction caused by hybridization.
s band 361 The band formed by the overlap of s orbitals.
semiconductor 360 A substance in which conductivity increases as the temperature increases.
sigma bond 335, 346 A valence bond wavefunction with cylindrical symmetry around the internuclear axis.
sigma electron 343 An electron that occupies an sigma orbital.
sigma orbital 343 A molecular orbital that resembles a s orbital when viewed along the internuclear axis. More precisely, it is so called because an electron that occupies a sigma orbital has zero orbital angular momentum around the internuclear axis, just as a s electron has zero orbital angular momentum around the nucleus.
sp hybridized 339 A hybrid orbital built from one s orbital and one p orbitals. Two p orbital remains unhybridized in this configuration.
sp2 hybrid orbital 339 A hybrid orbital built from one s orbital and two p orbitals. One p orbital remains unhybridized in this configuration.
sp3 hybrid orbital 339 A hybrid orbital built from one s orbital and three p orbitals.
superconductors 360 Substances that conduct electricity without resistance.
superimpose 335 Add together two or more items, generally graphs/plots.
trial wavefunction 341 An arbitrary wavefunction used in the variation theorem.
valence bond theory 335 A theory in which a bond is formed when an electron in one atomic orbital pairs its spin with that of an electron supplied by another atomic orbital.
valence orbitals 347 The orbitals of the valence shell.
valence theory 333 The theory of the origin of the numbers, strengths, and three-dimensional arrangements of chemical bonds between atoms.
valence-shell electron pair repulsion 334 A simple model of molecular shape based upon the repulsion between electron pairs.
variation theorem 341 If an arbitrary wavefunction is used to calculate the energy, then the value calculated is never less than the true energy.
virtual orbitals 347 The orbitals of an atom that are unoccupied in the ground state.
*All page numbers are from Atkins, The Elements of Physical Chemistry, Second Edition


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