final exam review Flashcards
what are sp hybrid orbitals
orbitals formed by mixing one s and one p orbital of a central atom
what is hybridization
a theoretical process of orbital mixing to form hybrid orbitals
what does the formation of bond orbitals mean
the wave functions of the electrons are in phase
what is the basic principle of valence bond theory
a covalent bond forms when orbitals of two atoms overlap and a pair of electrons occupy the overlap region
what does greater electronegativity difference result in
larger partial charges and higher partial ionic character
what is ON equal to
the number of valence electrons minus the number of shared electrons plus the number of unshared electrons
what is an oxidation number
the charge that an atom would have if all of the atoms attached to it were removed along with the electron pairs it is sharing with other atoms
electronegativity is ________ related to atomic size. why?
inversely related. the nucleus of a smaller atoms is closer to the shared pair than the nucleus of a larger atom
in substances what are most atoms joined by
polar covalent bonds, partly ionic and partly covalent
what makes a good fuel
covalent compounds with weak bonds and relatively less O
what is a fuel
a material that reacts with atmospheric oxygen to release energy
what is delta H r related to
sigma delta H reactant bonds broken + sigma delta H product bonds formed or sigma BE reactant bonds broken minus sigma BE product bonds formed *these are only for gas phase reactions
are covalent substances generally good conductors
no, electrons are localized and no ions are present
do molecular covalent substances have high melting and boiling points
no they have low mp and no because they have strong bonding forces between atoms within the molecule and weak intermolecular forces between separate molecules
do network covalent solids have a high melting and boiling points? why?
yes due to the large amount of energy required to rearrange covalent bonds
the trend in bond lengths is __________ to the trend in bond energy
opposite
as we go left across a group what does bond length do
increases
what does a higher bond order result in
a shorter bond length and higher bond energy
strong bonds are ______ in energy while weaker bonds are __________ in energy
lower, higher
why is bond energy always positive
bond breakage is an endothermic process
what is electron affinity
the energy change accompanying the addition of 1 mol of electrons to 1 mol of gaseous atoms of ions
what does the magnetic quantum number prescribe
the 3-d orientation of the orbital in the space around the nucleus
what are orbitals
mathematical solutions to the schrödinger wave equation
what are orbitals
mathematical solutions to the schrödinger wave equation
what does a higher nuclear charge do
it increases nucleus-electron attractions, lowering sub shell energy and stabilizing the atom
what is special about hydrogen and it’s energy state
it’s the only atom whose energy state depends completely on the principal quantum number
what does the principal quantum number specify
the energy level (shell) of the H atom, the higher the n value the higher the energy level
what is the principal quantum number
a positive integer that indicates the relative size of the orbital and therefore the relative distance from the nucleus of the peak in the radial distribution plot
what is psi (trident)
the wave function
what is the angular momentum quantum number related to (L)
the shape of the orbital
what is the major consequence of the exclusion principle
an atomic orbital can hold a maximum of two electrons and they must have opposing spins
what does penetration do
it increases the average effective nuclear charge for its electron and it decreases the shielding of a 2s electron by the 1s electrons
what does each solution to shrodingers equation give
an energy state associated with a given atomic orbital
:(
:(
what do transition metals lose first s or d electrons
s
what species are paramagnetic and what do they do
they are species with 1 or more unpaired electrons; they are attracted by an external magnetic field
elements in the same group have similar _______ and similar patterns of _______
valence electron configurations and reactivity
what are diamagnetic species and what do they do
they are species with all electrons paired, they are slightly repelled by an external magnetic field
are cations larger or smaller than parent atoms
smaller
are anions larger or smaller than parent atoms
larger
what do main group s block metals do
lose all electrons with the highest n balue
where do non metals gain electrons
in the p orbitals of the highest n value
what is penetration
the process by which an outer electron moves through the region occupied by the outer electrons to spend part of its time closer to the nucleus
what is the exclusion principle
no two electrons in the same atom can have the same four quantum numbers
which electrons are removed first from main group metals p or s
p
what does metallic behavior do across a period and down a group
in increases from right to left and down
what do elements that have low IEs and less negative EAs tend to do
lose electrons easily but attract them weakly
t/f elements that have high IEs and highly negative EAs tend to lose electrons with difficulty and attract them strongly
T
what does ionization energy do down a group? across a period?
decreases, increases
why does IE increase the more electrons you pull away
you are pulling electrons from a more and more positive ion
t/f ie2> ie1
t ALWAYS
what is ionization energy
the energy required to completely remove 1 mol of electrons from 1 mol of gaseous atoms or ions
as period number increases what happens to zeff
it rises significantly
which element is the biggest? the smallest?
Fr, F
what happens as zeff increases
outer electrons are pulled closer to the nucleus
what is bond energy
the energy needed to overcome the attraction between the nuclei and shared electrons, it is defined as the standard enthalpy change for breaking the bond in x mol of gaseous molecules
what is bond order
number of electron pairs being shared by a given pair of atoms
where is is the greater electron density in a covalent bond
between the nuclei
what causes a covalent bond
the balance between nuclei attracting the electrons and the electrons and nuclei repelling each other
what is the main way atoms interact
sharing electrons
why do ionic compounds have high mp and bp
large amounts of energy are required to free ions from their positions and separate them
when do ionic compounds conduct electricity
when melted or dissociated where ions can move and carry a current
what are typical physical behaviours of ionic compounds and why do they have these behaviours
they are hard (they do not dent), brittle (crack without deforming), and they are rigid (do not bend). there are strong attractive forces holding ions in specific positions
what does delta H lattice =
(cation charge * anion charge)/(cation radius + anion radius)
lattice energy is __________ to electrostatic energy
directly proportional
t/f there are periodic trends in lattice energy
t
what is lattice energy
the enthalpy change that accompanies the reverse of the equation of formation
is energy absorbed or released during electron transfer
absorbed
what form of matter are ionic compounds typically
solid
do 100% ionic or covalent bonds exist?
no, gradations of each type of bond occur
are electrons in metallic bonding localized or delocalized
deloacalized, they move freely throughout the piece of metal
in metallic bonding what is the metal iron core comprised of
nucleus plus inner electrons
what happens during metallic bonding
the enormous number of atoms in a sample of metal “pool” their valence electrons into a “sea” of electrons between and around each metal ion core
how does covalent bonding occur
the nucleus of each atom attracts the valence electrons of the other, drawing the atoms together
where does covalent bonding commonly occur
between non-metal atoms
what occurs during ionic bonding
electron transfer
where does ionic bonding occur
between atoms with large differences in electronegativity (usually between groups 1/2 and 17/the top of 16
what are resonance structures
two or more lewis structures for a molecule that cannot be adequately depicted by a single structure
what is electron pair deloaclization
the process by which electron density is spread over several atoms rather than remaining between the two atoms
what is a resonance hybrid
the weighted average of the resonance structures of a molecule
what is formal charge
the hypothetical charge on an atom in a molecule or ion, equal to the number of valence electrons minus the sum of all the unshared and half of the shared electrons
is formal charge the same as oxidation number
no
what are the electron deficient atoms
Be or B
what are free radicals
molecular or atomic species that contain one or more unpaired electrons which typically make the species very reactive
what do most free radicals have
1) a central atom from an odd numbered group
2) a lone electron (this makes them paramagnetic)
what are expanded valence shells
valence shells can accommodate more than 8 electrons by using available d orbitals
when can expanded valence shells occur
only with central non-metal atoms from period 3 or higher
when does the bond angle not equal the ideal angle
when there are double or triple bonds, when there are different elements, or when there is a lone pair
what does AXmEn represent
A- central atom
X- surrounding atom
E- non-bonding valence electron groups
what is the difference between electron group arrangement and molecular shape
-electron group arrangement is defined by bonding and nonbonding electron groups
-molecular shape is defined but the relative positions of the nuclei which are connected by bonding groups only
what are metals good conductors of
electricity and thermal energy
why do metals dent and bend
the metal cations are able to slide past each other in the “electron-sea” and end up in new positions
what are alloys
mixtures that have metallic properties and consist of solid phases of two or more pure elements, a solid-solid solution or distinct intermediate phases
which atoms will have more stable AOs
atoms with greater effective nuclear charge
what is the effect of s and p orbital mixing
lower energy of the sigma 2s and anti sigma 2s
in general the higher bond order the _______ the bond
stronger
what is molecular orbital bond order
number of electrons in bonding MOs minus the number of antibonding MOs divided by 2
what do electrons in an antibonding molecular orbital do
destabilize the molecule
what is an antibonding molecular orbital
formed when wave functions are subtracted from each other decreasing the electron density between the nuclei and leaving a node
what is MO theory
molecular orbital theory; describes a molecule as a collection of nuclei and electrons in which the electrons occupy orbitals extending over the entire molecule
where do pi bonds occur
side to side overlap
where do sigma bonds occur
end to end overlap
when does hybridization not apply
to large non metal hydrides
what shape does sp3d2 apply to
octahedral
what shape does sp3d apply to
trigonal bipyramidal
what shape does sp3 apply to
tetrahedral
what shape does sp2 apply to
trigonal planar
what shape does sp apply to
linear
what are properties of gasses
they are highly compressible, thermally expandable, they have low viscosity and density, and they are infinitely miscible
what are properties of an ideal gas
they have, negligible particle volume, many particles in random motion, particles colliding with each other and container walls, particles experience non interparticle forces, and the average kinetic energy of particles is directly proportional to the temperature of the gas
what is urms
root mean squared speed equals the square root of u bar squared
what does u bar squared equal
3RT/M
do gasses really move at typical speed in bulk
no, individual particles are moving in all different directions, they collide with each other and change direction which slows them down
what does temperature measure
the degree of random motion in a gas
does temp have meaning for one particle
no it is a statistical measure and thus only meaningful for large numbers of particles
what happens when we have 0 temperature
all translational motion ceases, however rotation and vibration can occur
what conditions do we see ideal and non ideal behaviour of gases
ideal: low p high t
non-ideal: high p low t
what causes non-ideal gases?
interparticle attraction
what does P =
nRT/(V-nb) - a(n/v)^2
in the van der waals equation what is a proportional to and b proportional to
a- interparticle forces
b- particle volume
what do particles look like in a gas?
particles are far apart and moving randomly
what do particles look like in a solid
they are close together and in an ordered arrangement
what do particles look like in a liquid
they are close together but randomly oriwnted
when we go from s-l-g energy is _____
what about g-l-s?
s-l-g: absorbed
g-l-s: released
what is sublimation
solid to gas - delta H subl
what is vaporization
liquid to gas - delta H vap
what is fusion
melting, solid to liquid, delta Hfus
what is condensation
gas to liquid- negative delta H vap
what is freezing
liquid to solid, negative delta H fus
what is deposition
gas to solid, negative delta H subl
what does the magnitude of delta H reflect
the strength of interparticle forces
why is delta H fus much less than delta H vap in general
much more energy needs to be absorbed to disrupt the IMFs and to separate particles far apart going from liquid to gas
when are phase changes reversible
in closed systems where they are equilibrium processes
when are phase changes not reversible
in open systems
what is the vapour pressure of a liquid
the constant pressure at the dynamic equilibrium where the rate of vaporization matches the rate of condensation
what does vapour pressure depend on
the type of liquid and the temperature
why does higher temperature increase vapour pressure
more particles move faster exceeding the threshold speed to escape into gas phase
what do substances with weaker intermolecular forces in the liquid have
higher vapour pressures and low boiling points
when does boiling occur
when the vapour pressure equals the external pressure
what is the normal boiling point
the temperature at which the vapour pressure is 1 atm
why does pressure have little effect on melting points
solids and liquids are nearly incompressible
what is happening at the melting point
a dynamic equilibrium between solid and liquid phases
when will a solid sublime
when IMFs are too weak to keep particles together when they leave the solid
what is present at the triple point
solid liquid and gas
what is a supercritical fluid
occurs starting at the critical point, it is when the densities of liquid and gas become equal- we cannot distinguish between them
is a supercritical fluid a mixture of solid and gas
NO
what do intermolecular forces influence
the physical properties of a substance
where are there no molecules
in simple ionic solids and extended network solids
what are interparticle forces primarily based on
electrostatic attractions
what is generally the strongest IMF? the weakest?
strongest- ion dipole
weakest- london dispersion (induced dipole dipole)
why are ion dipoles strong
they have a full ion charge involved
where do ion dipole forces arise
between ions and nearby polar molecules
where do dipole dipole forces arise
between polar molecules, where dipoles are aligned to maximize attractions
where do hydrogen bonding forces occur
between molecules that have H bonded to NOF
why are hydrogen bonds strong
1) the difference in electronegativity is particularly large for N-H O-H and F-H
2) hydrogen is a small atom which allows the close approach of other dipoles
what produces an induced dipole
shifts in electric field strength often produced by shifts in electron density
when do induced dipole induced dipole forces arise
between non polar molecules or single atoms
what is polarizability
the ease with which the electron cloud can be distorted to create a charge separation
what increases polarizability
greater number of electrons and larger molecule size
which is more polarizable cations or anions
anions because they have more electrons
polarizability _______ down a group and _______ across a period
increases down a group and decreases across a period
what does surface tension refer to
the resistance of a liquid to increase its surface area
what does high surface tension imply
strong intermolecular forces
what does capillarity refer to
the rising of liquid in a tube
what is wetting
the spreading of a liquid across a surface
what are cohesive forces
the forces within a liquid
what are adhesive forces
the forces between the liquid and the tube or surface
what happens to a liquid in a tube when cohesive and adhesive forces are similar in strength and character? different?
similar: the liquid is drawn up the tube
different: the liquid is not attracted to the tube
what is viscosity
the resistance of a liquid to flow
what does a high viscosity imply
high IMFs
what happens to viscosity of a motor when temperature increases
the viscosity decreases as HC carbon chains are disentangled
in XW30 what does a higher X value imply
more viscous oil
what is the solute
the minor component
what is the solvent
major component
what is a good guideline for solubility
“like dissolves like”
which electrons are involved in forming compounds
valence electrons
what are outer electrons
those in the highest energy shell, they spend most of their time furthest from the nucleus
what are core electrons
those that an atom has in common with the previous noble gas and any completed transition series, they fill all lower-energy shells of an atom
what are half filled and filled sub shells
unexpectedly stable
which subshell is more staple 2s or 2p
2s, it penetrates closer to the nucleus
what does a lower nuclear charge do
makes the electron easier to remove
what does shielding do
it reduces the full nuclear charge to an effective nuclear charge
what are the two types of shielding
1) shielding by other electrons in a given shell
2) shielding by electrons in inner shells
what are the two types of shielding
1) shielding by other electrons in a given shell
2) shielding by electrons in inner shells
how many possible orientations does a d orbital have
5
what is a 90% probability contour
the shape that the electron is within 90% of the time
how well can an electrons position be known
with a certain probability
as _______ increases, the probability that outer electrons spend most of their time farther from the nucleus increases
size
as we move down a group what happens
n dominates and increases
why does shielding occur
each electron feels both attraction to the nucleus and repulsion from other electrons, those repulsions counteract the nuclear attraction to a degree
what are lobes
regions where it is highly probable to find an electron
can we assign a definite size to an atom
no, the probability of finding an electron anywhere away from the nucleus is never 0
what is the trident squared
probability density, a measure of the probability of finding the electron in some tiny volume of the atom
what does removing an electron require
energy to overcome electrostatic attraction, IE is always positive
what is electronegativity
the ability of an atom in a bond to attract electron density towards itself
what is black body radiation
light given off by a hot idealized object that absorbed all of the radiation incident on it
what is the lowest possible energy of a d subshell
3d
the energy of an atom is quantized meaning?
it occurs in fixed quantities rather than being continuous
what is an electron density diagram
an electron-cloud depicition
what is the p orbital
the dumbbell or peanut shaped orbital
what does the fourth quantum number describe (ms)
spin
by convention what is the spin assigned to the first electron orbital
+1/2
what is the s orbital
the spherical shaped orbital
where does probability peak at (electron location)
near, but not at the nucleus
what is a quantum
the definite amount of energy an atoms absorbs/emits when changing energy levels
what is an orbital
a mathematical function that describes the electrons matter-wave (the three-dimensional space in which the highest probability exists of finding an electron)
why do electrons have certain allowable energies and frequencies
because electrons have wave-length motion in orbitals of fixed radii
what does the magnetic quantum number prescribe
the 3-D orientation of the orbital in the space around the nucleus
what is electron affinity
the energy change accompanying the addition of 1 mol of electrons to 1 mol of gaseous atoms or ions
what is urms =
sqrt(3RT/M)
