Chapter 1 Flashcards
the region where electrons reside is the
extranuclear space
shells define the probability of … in various regions of space relative to the …
finding an electron; nucleus
the energy of electrons in the shells is …, which means that only specific values of energy are possible,r ather than a continuum of values
quantized
delocalization: the spreading of electron density over a larger …
volume of space
each shell can contain up to … electrons
2n^2 (n is number of shell)
electrons in the first shell are nearest to the positively charged nucleus and are held most strongly by it; these electrons are
lowest in energy
orbital: region of space that can hold … electrons and has a specific quantized energy
two
orthogonal: having no net
overlap
the electron configuration of an atom is a description of the … its electrons occupy
orbitals
according to the pauli exclusion principle, for two electrons in the same orbital, their spins must be …
paired
electrons have a quantum mechanical property referred to as spin. they have magnetic north and south poles. two electrons with opposite spins are said to have
paired spins
orbitals of equal energy are called
degenerate
the reason hund’s rule stands (electrons fill orbitals individually before doubly) is because of
electron-electron repulsion
hund’s rule also states that the spins of the single electrons in the degenerate orbitals should be
aligned
unstable structures possess energy waiting to be released. when a structure is higher in energy, the more energy it has
stored
all of nature seeks its … energy state; when electrons are rearranged back to their ground state, energy is …
lowest; released
the energy it takes to remove an electron from an atom or a molecule is called the …
ionization potential
ionization potential … across a period and … a group
across; up
an atom that gains electrons becomes an … and an atom that loses electrons becomes a ..
anion; cation
when atoms are held together primarily by …, we say that an ionic interaction exists between them
attraction of oppositely charged ions
Electronegativity increases as … increases, and does so … a period and … a group
Zeff; across; up
the energy released upon addition of an electron is called the …, which becomes more favorable as you move from … to … in a row of the periodic table
electron affinity; left; right
because the electronegativity of an atom reflects its tendency to hold on to and to acquire electrons, the phenomenon arises from a combination of … and …
ionization potentials; electron affinities
the attraction between ions is what permits ionic salts to form a strong … and gives them a high ..
crystal lattice; melting point
according to the lewis model, a pair of electrons in a covalent bond functions in two ways simultaneously: it is shared by two atoms and at the same time fills the … of each
outer shell
bond dissociation enthalpy is the energy that would have to be absorbed to
break a bond
when bonds are formed by the sharing of two electrons between adjacent atoms, the system becomes more stable because the … of the electrons is stablilized relative to two separate atoms. the wave that represents the electrons in a bond is partially concentrated in the space …, leading to … between them. in contrast, they are attracted to each … and shield the … between the two nuclei
wave character; between the nuclei; repulsion; nucleus; repulsion
the lowering of the energy of the wave character of the electrons along with their added attraction to each nucleus is balanced with the … between the … and the …. This balance results in an optimum … called the …
repulsion; nuclei; electrons; internuclear distance; bond length
the distance between nuclei participating in a chemical bond is called the
bond length
a good way to distinguish covalent bonds from ionic attraction is the fact that covalent bonds have defined … and … resulting from the … of electrons
geometries; connectivities; sharing
the polarity in the bond increases with increasing … between the bonded atoms
difference in electronegativity
nonpolar covalent is less than ..
polar covalent is less than/equal to … and greater than/equal to …
ionic is greater than …
0.5; 1.9; 0.5; 1.9
electronegativity varies somewhat depending on the …. and … state of an atom
environment; oxidation
in particular, carbon in compounds is not atomic carbon, and it often behaves as if its electronegativity is … than that shown
greater
the polarity of a covalent bond is measured by a vector quantity called a …, defined as the product of the …, e, on one of its atoms times the …, d, separating the two atoms
bond dipole; charge; distance
the charge on an atom in a molecule/polyatomic ion is called its
formal charge
formal charge = number of … - (all … electrons + 1/2 all … electrons)
valence e-; unshared; shared
when an atom possessing an octet of electrons has one bond more than its neutral state, the atom is … charged; when it has one bond less than its neutral form, it is … charged
positively; negatively
for group 3A elements, their valence shells are only … filled. trivalent compounds of boron and aluminum exhibit a high … with compounds that have extra …, enabling them to fill their octets
these elements don’t have 8 electrons after bonding
partially; reactivity; electrons
dative/coordinate covalent bonds: where the two electrons come from only a … or … while the other involved in that bond does not contribute any electrons
single group; atom
functional groups allow us to divide organic compounds into classes, and exhibit characteristic …
chemical reactions
unshared pairs of electrons are generally …. in a condensed structural formula
not shown
alcohols are classified as primary, secondary, or tertiary depending on the number of … bonded to the …
carbon atoms; carbon bearing the OH group
in a primary amine, nitrogen is bonded to …, in a secondary amine, it’s bonded to …, in a tertiary its bonded to …
one carbon; two carbons; three carbons
aldehydes and ketones both have .., but aldehydes contain …, where ketones contain the … group bonded to …
carbonyl; CHO group; carbonyl; two carbons
in a condensed structural formula, carboxyl can be written as … or …
COOH; CO2H
a carboxylic ester, is a derivative of a carboxylic acid in which the hydrogen of the carboxyl group is replaced by a ..
carbon-containing group
a carboxylic amide is a derivative of a carboxylic acid in which the … is replaced by an …
OH; amine
VSEPr stands for
valence-shell electron-pair repulsion
tetrahedral: a bonding arrangement in which an atom is bonded to … atoms located at the corners of a …
four; tetrahedron
pyramidal: a bonding arrangement in which an atom is bonded to three atoms in a
triangular pyramid
discrepancies between predicted and observed angles can be explained by propsoing that unshared electron pairs repel … pairs more strongly than do bonding pairs
adjacent
to predict whether a molecule is polar, we need to determine whether it has … and what the … of its atoms is in space
polar bonds; arrangement
the molecular dipole moment of a molecule is the vector sum of its individual
bond dipoles
neither lewis model or vsepr gives any means of accounting in a quantitative way for the reasons atoms combine in the first place to form … with the …
covalent bonds; liberation of energy
each wave function psi is associated with a unique set of quantum numbers and with a particular atomic or molecular … A wave function occupies 3d space and is called an …, which can contain no more than two electrons
orbital; orbital
psi squared is proportional to the probability of finding an electron at a
given point in space
the value of psi squared at any point in space is proportional to the … at that point
electron density
although the value of psi at any point can be positive/negative, the value of psi squared will always be positive in an orbital. In other words, the electron density in two regions of an orbital will be equal if those regions have the same absolute value of …
psi
when we describe orbital interactions, we are referring to interactions of …, which interact … or …
waves; constructively; destructively
phasing: the sign of the … at particular coordinates in space, either plus or minus
wave function
the greater electron density is on the more …, especially those with …
electronegative atoms; lone pairs
the valence bond approach to approximating the energetics of covalent bond formation provides the most easily visualized description of …, while the molecular orbital method is most convenient for describing ..
.single bonds; multiple bonds
molecular orbital theory begins with the hypothesis that electrons in atoms exist in atomic orbitals and assumes that electrons in molecules exist in …
molecular orbitals
the number of molecular orbitals formed is equal to the number of
atomic orbitals combined
just like atomic orbitals, molecular orbitals are arranged in order of
increasing energy
when electrons occupy a sigma bonding molecular orbital, electron density is concentrated in the region between the two … and serves to offset the repulsive interaction between them
positively charged nuclei
a bonding molecular orbital is an orbital in which electrons have a … energy than they would in the isolated atomic orbitals
lower
sigma bonding molecular orbitals are … about the axis
cylindrically symmetric
out-of-phase addition: … of the wave functions of two orbitals
subtraction
antibonding molecular orbital: an orbital in which the electrons in it have a … energy (are more easily …) than they would have in the isolated atomic orbitals. Population of this orbital with electrons actually causes … involved
higher; removed; repulsion of the nuclei
a key feature of MO theory is that molecular orbitals extend over … because all of the orbitals of all the atoms take part in constructing molecular orbitals. A second key feature is that the molecular orbitals are created by the … and … addition of all the atomic orbitals that are aligned to overlap on all atoms in a molecule
entire molecules; in phase; out of phase
a basic principle of valence bond theory is that bonds are created by the … of atomic orbitals on .. therefore, with vb theory, the bonds are … between adjacent atoms rather than …. over several atoms as in MO theory
overlap; adjacent atoms; localized; delocalized
to account for the observed bond angles in a way that is intuitive for hemists, linus pauling proposed that atomic orbitals for each atom should be thought of as … to form new atomic orbitals, called …, which then interact to form bonds by overlapping with orbitals from other atoms
combining; hybrid orbitals
hybrid orbitals are formed by combinations of atomic orbitals, a process called … mathematically, this is accomplished by combining the wave functions of the … and three … orbital wave functions. the number of hybrid orbitals formed is equal to the number of …
hybridization; 2s; 2p; atomic orbitals combined
sp3 hybridization results in bond angles of approximately … each sp3 orbital has …% s character and …% p character
109.5 degrees; 25; 75
superscripts in the designation of hybrid orbitals tell you how many … have been combined to form the hybrid orbitals
atomic orbitals
the angle between sp2 hybrid orbitals is …
120 degrees
sp hybrid orbitals lie at an angle of …
180 degrees
sp has …% s character and …% p character
50; 50
S and P, which tend to have more bonds than allowed by the octet rule are considered to be … hybridized with ..
sp3; formal charges
combining MO and VB:
valence bond theory gives the experimentally determined geometries through … and viewing bonding as arising from electrons localized between adjacent atoms. MO contributes through the … and … addition of the orbitals
hybridization; in; out of phase
one resulting molecular orbital is lower in energy than the two separate atomic orbitals and is called the … orbital. The other resulting molecular orbital is higher in energy than the two atomic orbitals and is … Only the …. orbital is populated
bonding sigma; antibonding; lower energy
wherever there is a double bond, …. hybridization should be considered for the atoms involved
sp2
the combination of parallel 2p atomic orbitals by in phase and out of phase addition of their wave functions gives a … and … molecular orbital
pi bonding; pi antibonding
When C, N, and O have an octet of electrons and are involved in making only single bonds to other atoms, these atoms are … hybridized
sp3
when c, n, and o, have an octet of electrons and are involved in double bonds, these atoms are … hybridized unless the atom makes two double bonds; in which case they are .. .hybridized
sp2; sp
finally, when c, n, and o have an octet of electrons and are involved in triple bonds, they are … hybridized
sp
atombs bonded to only one other atom (called a terminal atom) are not assigned a …
geometry
atoms with sp3 hybridization adopt …., …, or … geometries depending on whether they are bonding to …,…, or … other atoms respectively
four; three; bent
atoms with sp2 hybridization adopt … or … geometries depending on whether they are bonded to three or two other atoms, respectively. atoms with sp hybridization adopt only … geometries
trigonal planar; bent; linear
individual lewis structures are called … or …
contributing structures; resonance structures
the real molecule or ion is a … of the various contributing structures
resonance hybrid
a curved arrow is nothing more than a bookkeeping symbol used to keep track of electron pairs, or as some call it, …
electron pushing
when you draw curved arrows to indicate the creation of a new contributing structure, the arrows always start on either a … (or …) or a …, and should end at an atom that can … or should create a … on an atom
double; triple bond; lone pair of electrons; accept a bond; lone pair of electrons
acceptable contributing structures: must have the same number of ... must obey the rules of covalent bonding positions of all nuclei must be the ... must have the same number of ... and ... electrons
valence electrons; same; paired; unpaired
characteristics of more contributing structures:
structures in which all atoms have ….
maximum number of … (less unpaired …)
fewer …
negative charge is on a more … and positive charge is on a less …
completed octets; covalent bonds; electrons; formal charges; electronegative atom; electronegative atom
if resonance structures contribute unequally, the actual structure of the hybrid most resembles the structure that
contributes most
delocalization is always a … effect
stabilizing
conjugation: lack of atoms between … or btween … and … electrons
pi bonds; pi bonds; lone pair
to picture the orbitals involved in delocalized systems, we use only
mo theory
because we consider delocalization only for molecules containing pi bonds adjacent to pi bonds and/or pi bonds adjacent to lone pairs, we only use … for such systems
MO theory
for an atom to be involved in pi bonding, it must have a … orbital
2p
triple bonds are … and … than double bonds
shorter; stronger
relative lengths of C H bonds are determined by the percent … in the hybrid orbital of carbon forming the sigma bond with hydrogen. the greater the percent, the .. electrons in it are held to the nucleus and the … the bond
s character; closer; shorter
there is correlation between bond length and strength: the shorter the bond, the … it is
stronger
