Organic 1: Structure Determines Properties Flashcards by Shannon Faulkenberry

Atomic number Z

each element is characterized by this, which is equal to the number of protons in its nucleus

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Wave functions

mathematical descriptions of the electron wave, symbolized by Greek letter psi; AKA orbitals

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Psi^2

probability of finding an electron at a particular spot relative to an atom’s nucleus = psi^2 at that point

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Principal quantum number n

letter s is preceded by this, which specifies the shell and is related to the energy of the orbital

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Shell

group of orbitals that have the same principal quantum number n

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Boundary surfaces

more common to represent orbitals by these; encloses the region where the probability of finding an electron is high (90-95%)

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Spin

synonymous with spin quantum number

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Spin quantum number

can have a value of +1/2 or -1/2

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Pauli Exclusion Principle

two electrons may occupy the same orbital only when they have opposite (paired) spins; for this reason, no orbital can contain more than 2 electrons

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Period

row of the periodic table; corresponds to the principal quantum number of the highest numbered occupied orbital

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Nodal surfaces

regions of a single orbital may be separated by these where the wave function changes sign and the probability of finding an electron is zero

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Hund’s Rule

general principal for orbitals of equal energy; when 2 orbitals are of equal energy, they are populated by electrons so that each one is half-filled before either one is doubly occupied

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Valence electrons

outermost electrons, the ones most likely to be involved in chemical bonding and reactions

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Valence shell

the group of orbitals, filled and unfilled, responsible for the characteristic chemical properties of an atom

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Main-group elements

for these, the number of valence electrons is equal to its group number in the periodic table

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Octet

having 8 electrons in the valence shell

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Noble (rare) gases

helium, neon, and argon are in this class; characterized by extremely stable, “closed-shell” electron configuration; very unreactive

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Compounds

atoms combine with one another to give these, having properties different from the atoms they contain

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Chemical bond

attractive force between atoms in a compound

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Ionic bond

force of attraction between oppositely charged species (ions)

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Cations

positively charged ions

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Anions

negatively charged ions

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Isoelectronic

species that have the same number of electrons

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Ionization energy

large amount of energy that must be transferred to any atom to dislodge an electron

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Endothermic

processes that absorb energy

Exothermic

energy-releasing reactions; energy change for this process has a negative sign

Electron affinity

energy change for addition of an electron to an atom

Electrostatic

attractive forces between oppositely charged particles; AKA coulombic attractions; what is meant by an ionic bond between 2 atoms

Covalent (shared electron pair) model

first suggested by GN Lewis (1916); proposed that a sharing of 2 electrons by 2 hydrogen atoms permits each one to have a stable, close-shell electron configuration analogous to helium

Lewis structures

structural formulas in which electrons are represented as dots; customary to represent a shared electron-pair bond by a dash

Bond dissociation enthalpy

amount of energy required to dissociate a hydrogen molecule H2 to two separate hydrogen atoms

Unshared pairs

Valence electrons not involved in bonding

Octet rule

in forming compounds, elements gain, lose, or share electrons to achieve a stable electron configuration characterized by 8 valence electrons

Double bond

bond formed by the sharing of 4 electrons between 2 atoms

Triple bond

bond formed by the sharing of 6 electrons between 2 atoms

Polar covalent

if one atom has a greater tendency to attract electrons toward itself than the other, the electron distribution if polarized and the bond is described at this

Electronegativity

tendency of an atom to attract the electrons in a covalent bond toward itself

Electrostatic potential map

uses the colors of the rainbow to show charge distribution

Bond dipole moments

exists whenever opposite charges are separated from each other; direction of this is toward the more electronegative atom

Dipole moment mu

product of the amount of the charge e multiplied by the distance d between the centers of charge (mu = e x d)

debye (D)

unit customarily used for measuring dipole moments; 1D = 1 x 10^-18 esu cm

Formal charges

the charge, either positive or negative, of an atom calculated by subtracting the number of valence electrons in the neutral atom a number equal to the sum of its unshared electrons plus half the electrons in its covalent bonds

Molecular formula

tells us which atoms and how many of each are present in a compound

Connectivity

order in which atoms are connected

Isomers

different compounds that have the same molecular formula

Constitutional isomers

isomers that differ in connectivity; AKA structural isomers

Stereoisomers

isomers that differ in arrangement of atoms in space

Resonance

when 2 or more Lewis structures that differ only in the distribution of electrons can be written for a molecule, no single Lewis structure is sufficient to describe its true electron distribution

Resonance hybrid

the collection of Lewis structures that, taken together, represent the electron distribution in a molecule

Contributing structures

the various resonance structures that can be written for a molecule

Localized

Lewis formulas show electrons as this; they either are shared between 2 atoms in a covalent bond or are unshared electrons belonging to a single atom

Delocalized

electrons shared by several nuclei

Curved arrows

writing the various Lewis formulas that contribute to a resonance hybrid can be made easier by using these to keep track of delocalized electrons; converts 1 Lewis structure to another by moving electron pairs using these

Condensed formulas

leave out some, many, or all of the covalent bonds and use subscripts to indicate the number of identical groups attached to a particular atom

Bond-line formula

AKA carbon skeletal diagram; we assume that there is a carbon atom at every vertex and at the end of a line

Heteroatoms

atoms that are neither carbon nor hydrogen

Solid wedge

represents a bond that projects toward you

Dashed wedge

represents a bond that points away from you

Simple line

represents a bond that lies in the plane of the paper

Valence shell electron-pair repulsion (VSEPR) model

rests on the idea that an electron pair, either a bonded pair or an unshared pair, associated with a particular atom will be as far away from the atom's other electron pairs as possible

Tetrahedral angle

permits four bonds to be maximally separated; characterized by angles of 109.5 degrees; ex. water, ammonia, methane

Molecular dipole moment

resultant of all of the individual bond dipole moments of a substance

Double-barbed arrow

shows the movement of a PAIR of electrons, either a bonded pair or a lone pair

Single-barbed (fishhook) arrow

shows the movement of 1 electron

Acid

substance that ionizes to give protons when dissolved in water

Base

ionizes to give hydroxide ions

Acidity constant

equilibrium constant Ka; measures the strength of a weak acid

pKa

-log (base 10) Ka

Bronsted-Lowry acid

proton donor

Bronsted-Lowry base

proton acceptor

Conjugate acid

base and this differ by a single proton

Conjugate base

acid and this differ by a single proton

Oxonium ion

systematic name for the conjugate acid of water (H3O+)

Hydronium ion

common name for H3O+

Basicity constant Kb

Bronsted-Lowry approach involving conjugate relationships between acids and bases make this unnecessary

Inductive effects

structural effects that are transmitted through bonds

Strong acid

one that is stronger than H3O+

Weak acid

one that is weaker than H3O+

Strong base

one that is stronger than OH-

Lewis acid

electron-pair acceptor

Lewis base

electron-pair donor

Lewis acid/Lewis base complex

species that results by covalent bond formation between a Lewis acid and a Lewis base

Substitution

one atom or group replaces another in a reaction

Nucleophiles

nucleus seekers; Lewis bases that use an unshared pair to form a bond to some other atom

Electrophiles

electron seekers; Lewis acids

Organic 1: Structure Determines Properties Flashcards

(85 cards)