Unit 3
Covalent Network solid
network of hybridized covalent bonds -diamonds + graphite (Csolid), and glass (SiO2) -very high MP
Higher bond orders indicate __________________(more or less?) stable molecules?
more stable
What is the electronic geometry for a molecule with six RHEDs surrounding the central atom?
octahedral
How many forces exist between non-polar molecules?
one force between non-polar molecules: dispersion
The σ bonding orbital has zero nodes, whereas the σ* anti-bonding orbital has ___________node(s).
one node
Every double covalent bond has both one ___________________ and _______(how many?) pi bond(s).
one sigma and one pi!
Every triple covalent bond has a sigma and __________(how many) pi bonds in it.
one sigma, two pi bonds
Diatomic molecules (meaning composed of two atoms) only have _________bond, so the molecule polarity matches the polarity of the bond.
only have one bond
We can determine if a molecule has an overall dipole moment by analyzing the shape (symmetrical or not) of the molecule and the polarity of the bonds. If there is an overall separation of _________________, then the molecule is polar. If there is not an overall separation of charge, then the molecule is nonpolar.
overall separation of charge = molecule is polar
Amount of energy required to remove the second e- from an atom K+(g) → K2+(g) + e-
second ionization energy
4 bonds + 1 lone pair =
seesaw
Every single covalent bond is one __________________ bond.
sigma
If the anions and cations have a _________________electrostatic interaction (i.e. large charges), it will require a lot of energy to separate the solid into gaseous ions.
strong
cations have lost electrons. As a result they have both fewer electrons in the highest energy atomic orbitals farthest from the nuclei and the remaining electrons feel a _____________________ pull from the nucleus.
stronger
3 bonds + 2 lone pairs =
t-shaped
3 bonds + 3 lone pairs
t-shaped
Temperature of a liquid or solid and vapor pressure are__________________________ (inversely or directly?) related?
temp (of solid or liquid) and vapor pressure are directly related -temp of liquid increases, so does vapor pressure -As temperature (kinetic energy) increases, rate of evaporation increases and rate of condensation decreases. Therefore, vapor pressure will increase with increasing temperature.
Normal boiling point
temp. at which a liquid boils at 1 atm of pressure -most useful when comparing different liquids because boiling is affected by altitude and pressure
For liquids, higher temperatures correspond to higher average kinetic energies and faster moving particles. This will lead to a ______________________ (higher or lower?) viscosity.
lower
Consider two hydrogen atoms. Each hydrogen atom has one electron in its 1s shell. Are these two hydrogen atoms likely to form a bond? Yes! It is favorable for the two atoms to form a covalent bond, in order to achieve a full valence shell (i.e. ______________energy and a more stable system).
lower energy and a more stable system
LUMO
lowest unoccupied molecular orbital
paramagnetic
a molecule w/ at least one unPAIRed electron
diamagnetic
a molecule with no unpaired electrons
Does MO Theory fill up all sigma orbitals before all sigma star orbitals?
-YES bc MO Theory follows the Aufbau Principle! therefore electrons fill the orbitals of the lowest available energy levels before occupying higher levels
What kind of solid will carbon dioxide make?
-a MOLECULAR crystal/solid -CO2 is a covalent molecule. Any extended lattice among covalent molecules will be held together by intermolecular forces. In this case, carbon dioxide is held together with dispersion forces and dipole-dipole interactions. Covalent bonds are not found between CO2 molecules, only within the molecule. Therefore, the crystal will be molecular.
What is a molecular crystal, and how does it differ from a covalent crystal?:)
-biggest diff. is held by IMFs, not covalent bonds -molecules at the lattice points of the crystal, held together by relatively weak IMFs -in nonpolar crystals, disp. are IMFs -in polar crystals, dipole-dipole are IMFs -poor electrical conductors bc lacks ions or free e- -IMFs holding molecules together are much weaker than ionic or covalent bonds, so MP and BP of molecular crystals are low -good example is ice, held by H-bonds
In a covalent compound the electrons are shared between the atoms in the compounds. This "sharing" is not always equal. Instead the electrons are distributed about the entire molecule in such a way that _____(minimizes or maximizes?)_________ their energy compared to their energies in the separate atoms. The energy of the molecule is________________ (more stable) than the energy of the separated atoms.
-minimizes energy compared to their energies in the separate atoms -the energy of the molecule is more stable than the energy of the separated atoms
molecular solid characteristics
-molecules held by van der Waals forces -weak nature of IMFs -soft, volatile, low melting temperature, electrical insulators -Larger molecules are less volatile and have higher melting points because their dispersion forces increase with the larger number of atoms. Decrease in binding of outer electrons to the nucleus also increases van der Waals-type interactions of the atom due to its increased polarisability.
What are the common covalent network solids?
-pure Carbon (C): diamond, graphite, and buckyball -pure Silicon (Si) -Silicon Carbide (SiC) -quartz (SiO2)
1 RHED is equal to...
1 lone pair of electrons 1 single bond 1 double bond 1 triple bond
two ways that formal charge can help us:
1) It can help us decide which of several Lewis dot structures is closest to representing the properties of the real compound. 2) It can help us envision where there might be regions of positive or negative charge in a molecule.
Three concepts of MO theory
1. *All* atomic orbitals are considered when predicting bonding across the molecule 2. Atomic orbitals combine to form *molecular* orbitals 3. Electrons are *delocalized*
Three concepts of VB theory
1. The atomic orbitals *around the central atom* are considered when predicting bonding between atoms 2. Atomic orbitals combine to form *hybridized* orbitals 3. Electrons are *localized*
Any time a difference in electronegativity is greater than ___________, it is safe to consider that particular bond an ionic bond.
1.5
All molecules with tetrahedral molecular geometries have bond angles of ___________.
109.5 degrees
Consider the compound peroxyacetylnitrate, an eye irritant in smog. (look up Lewis structure) Predict the indicated bond angle.
120° Nitrogen is the central atom for the bond angle indicated.
Consider a 3-atom molecule A-B-A for which B has a total of only four valence electrons. If you assume that B is a Group II metal, what is the bond angle for A-B-A?
180 degrees A Group II metal has two valence electrons, therefore it can only form two single bonds. B will not have any lone pairs.
How many sigma and pi bonds are present in the molecule HCN?
2, 2
If a molecule has "permanent dipole movement," what kind of a molecule is it?
a molecule with permanent dipole movement is a polar molecule
carboxide
A compound of carbon and oxygen, such as carbonyl, with some element or radical. potassium carboxide
Regions of High Electron Density (RHEDs)
A region within a molecule where valence electrons can be found
When naming compounds w/ polyatomic ions, which comes first?
Always name the cation (metal) first!
free radical
Any molecule, ion, or atom with one or more unpaired electrons. They vary in reactivity and stability from highly reactive, occurring as transient (short-lived) species, to metastable.
For a molecule that has resonance structures in which single and double bonds are flipping, if we could do an experiment to measure the bond strength of those bonds... A. 50% of the time we would measure a single bond and 50% of the time we would measure a double bond B. every time the measurement would give the same bond strength close to the average of a single and double bond
B. every time the measurement would give the same bond strength close to the average of a single and double bond The second answer is correct. The first answer is a huge misconception in chemistry. The reason we draw resonance structures is *not because* the bonds in the molecule *can't make up their minds*, but rather because we *insist* on drawing structures with single and double bonds. *The real molecule is not flipping back and forth between these two but is always somewhere in between.*
surface tension
a property of liquids that arises bc the molecules at the surface of a liquid have higher energy than the molecules in the middle of the liquid
Is a C-S bond polar?
C-S bond is considered nonpolar because the EN difference is almost zero
oxalate
C2 O4
methane
CH4
Valence Bond (VB) Theory
Describes one way of picturing *how* the bonding occurs Describes the geometry predicted by VSEPR
_______________________________ describes the relative pull of the electrons in a covalent compound. A small atom with a large effective nuclear charge will be extremely ______________________________, whereas a large atom with a small effective nuclear charge will not be very ____________________________.
Electronegativity (electronegative)
Valence Shell Electron Pair Repulsion (VSEPR) Theory
Electrons repel other electrons They require "elbow space"
The first thing that trends show us is that the valence electrons for elements in each group are essentially the same. What does that mean?
Elements in the same group will have similar properties because they have similar electron configurations.
FC is _____ for neutral compounds
FC is 0 for neutral compounds
FC should_________charge on polyatomic ion.
FC should = charge on polyatomic ion
equation for formal charge (in my own words)
FC=(#of vse-) - [# of shared pairs + (# of e- in a lone pair) a lone pair is a pair of electrons that is not shared between two atoms it is kinda just hanging off of one atom
equation for formal charge (the one I don't like)
FC=V-(L + 0.5S) Where FC is the formal charge, V is the number of valence electrons, L is the number of lone pair electrons, S is the number of shared electrons
Why is HF not an ionic bond? What is it?
HF is a hydrogen bond -it is not ionic (even though it has an ENdiff of 1.9) BC Fluorine is exceptionally small (due to large attractive forces between e- and protons) so its magnitude of interelectronic repulsive forces dominates over attractive forces (electronegativity or electron affinity)
According to molecular orbital theory, which of the following is NOT predicted to exist? He He2+ He2- All are predicted to exist.
He2 Molecular orbital theory only predicts whether or not a bond will exist. When the bond order is equal to 0, a molecule is predicted to not exist.
Name the compound CaBr2
Hint: CaBr2 will be named using the ionic nomenclature. Remember that you only need to use roman numerals if the cation can take on multiple charge states. -calcium bromide When calcium forms ionic compounds, it has an oxidation state of +2. Since bromide has a -1 charge, you automatically know that two bromides are required for one calcium to balance the charges (+2 and -2). So, the "di" in dibromide is dropped, because Ca will always have a +2 charge in these cases.
________________________ atoms are always at the ends of a sequence of atoms.
Hydrogen
Why doesn't Hydrogen form ionic bonds and instead forms covalent bonds?
Hydrogen with an EN of 2.1 is not strong enough to steal electrons from other atoms NOR is weak enough so that other atoms steal electrons from it
Why is I2 a solid while H2 is a gas?
I2 is more polarizable than H2. -I2 has significantly more electrons than H2. In addition, those electrons are in orbitals that are significantly farther from the nucleus, making it easier to distort the electron cloud. In other words, I2 is more polarizable than H2. Higher polarizability leads to higher London dispersion forces. Neither molecule has a dipole nor can they perform hydrogen bonding.
Polar covalent bonds connect two atoms with differing electronegativities. The electrons are pulled toward the ______________ (more or less?)____ electronegative atom, resulting in one atom with a partial positive charge (δ+) and the other atom with a partial negative charge (δ-).
In a polar covalent bond, electrons are pulled toward the more electronegative atom (greater tendency to attract a shared pair of electrons to itself)
Which theory focuses on bonding throughout a molecule?
Molecular Orbital (MO) theory!
Which of the following atom pairs would share their electrons equally in a covalent bond (i.e. form a nonpolar bond)? Select all of the correct answers. nitrogen and nitrogen hydrogen and hydrogen hydrogen and fluorine fluorine and fluorine nitrogen and fluorine hydrogen and nitrogen
N2 F2 and H2 because there is no EN diff. between the composing atoms for any of those (bc the composing atoms are the same!) :)
Do the strength of bonds within a molecule have any affect on the strength of intermolecular forces?
NO the strength of bonds w/in a molecule has no affect on the strength of intermol. forces!
Which bond is most polar? Group of answer choices I‒Cl P‒I Cl‒Cl P‒Cl
P‒Cl differences across a period are greater than differences up and down a group
# of equivalent hybridized orbitals always equals # of ______________________.
Regions of High Electron Density
T/F All molecules have instantaneous dipoles.
TRUE bc all molecules have intermolecular forces!
What are three important contributions that MO theory makes to chemistry?
The ability to predict the energy at which a molecule will absorb light. The ability to predict whether or not a molecule should be paramagnetic or diamagnetic. The ability to use MO theory with a computer to calculate the minimum energy geometry of a molecule.
A chemist has synthesized two new dyes based on the molecular structure of plant-based dyes. The lowest energy absorption line for the first dye is light in the visible region at 530 nm. The lowest energy absorption line for the second dye is light in the visible region at 645 nm. Based on this evidence, which molecule has the larger HOMO-LUMO gap?
The dye that absorbs at 530 nm.
The sp3 hybridization has what percent s character and what percent p character respectively?
There are 4 orbitals being hybridized, 1 s orbital and 3 p orbitals. What percentage of the orbitals being hybridized are 's' and what percentage are 'p?' s = 1/4 = 25% p = 3/4 = 75%
T/F HCN can never exhibit resonance.
True HCN can never exhibit resonance because a double bond cannot form between hydrogen and carbon.
As the size of the atoms involved increase, so does a molecular attraction called the _____________________________ force. It is the result of electrons "bunching up" on part of a molecule. As one side becomes negative, the other turns positive, creating an attraction between molecules that makes them stick together.
Van der Waals
Why are metallic solids good conductors?
While metals are ductile and malleable (able to be formed into wires or pounded into sheets), they are also good conductors because *their electrons are delocalized* to form a "sea of electrons" that allow electrecity (the movement of electrons) to flow freely.
Is IF4- non-polar?
Yes, it is non-polar. Think about the molecular geometry of IF4-. Does the highly electronegative fluorine atoms cancel each other out?
hybridization
You can imagine the atoms combining their "pure" valence shell atomic orbitals (s, p, d, and f) to form a new set of orbitals to use in bonding.
In Lewis structures, a solid line is used to represent...
a covalent bond two electrons shared!
viscosity
a liquid's resistance to flow (molecules w/ branches or kinks have greater viscosity than straight-chin molecules)
If the anions and cations can pack tightly together (i.e. small ions), it will require __________________________(how much)?________energy to separate the solid into gaseous ions.
a lot of lattice energy to separate the solid into gaseous ions
covalent solid
all atoms connected w/ covalent bonds -hard -high melting points -insoluble in water
molecular solid
all molecules connected w/ weak IMFs (rather than held together by bonds) -brittle -low melting points -has localized electrons w/in the bonds in each molecule -> do not conduct electricity! -ex. Solid ice water
What electronegativity difference constitutes a polar covalent bond?
an EN difference between 0.4 and 1.7 or roughly 2.0 -below is pure or nonpolar -above is ionic
Bond Order = 1/2 (bonding electrons - ____________________ electrons)
antibonding
In order for a molecule to exhibit resonance, the Lewis structure must contain...
at least one double or triple bond.
The Molecular Geometry is the resulting shape of the___________________ that minimizes the repulsions between rheds
atoms
Electrostatic forces
attractive or repulsive forces between particles that are caused by their electric charges. This force is also called the Coulomb force or Coulomb interaction and is so named for French physicist Charles-Augustin de Coulomb, who described the force in 1795.
The boiling points of halogens __________________________ as their atomic radii increase.
boiling points of halogens increase as their atomic radii increase
If a central atom has fewer than _____ electrons (and it is not an exception to the octet rule) a multiple bond is likely. Move electrons from outer atoms to form multiple bonds. (double is 2 shared pairs, triple is 3 shared pairs)
central atom fewer than 8 electrons=multiple bond is likely
Ionic bonding typically occurs when it is easy for one atom to lose one or more electrons and another atom to gain one or more electrons. However, some atoms won't give up or gain electrons easily. Yet they still participate in compound formation. How?
covalent bonds by sharing electrons!
What is the predominant intermolecular force between IBr molecules in liquid IBr?
dispersion forces -You might have thought that dipole forces was right. The fact is that the dipole between iodine and bromine is incredibly weak- too weak to account for the fact that this compound is a liquid. Dispersion forces are actually the dominant forces here due to the SIZE of these atoms and, hence, the size of the molecule. Just know that not ALL dipole forces are bigger than any set of dispersion forces. Size matters, and dispersion forces win out here.
Very weak and very short range attractive forces between temporary (induced) dipoles are called...
dispersion forces.
Amount of energy released when an e- is added to an atom S(g) + e- → S-(g)
electron affinity
We can use ________________________ to quantify how much of a pull an atom has within a covalent bond.
electronegativity
Which of the following trends assume that the atom is bonded to another atom within a molecule? electron affinity electronegativity ionization energy atomic radius
electronegativity Electronegativity is the only periodic trend that assumes that the atom is within a molecule.
Which EN diff is typically greater? from group to group (across horizontally) or period to period (up and down)?
electronegativity difference is slightly more across horizontally from group to group than it is from period to period ex. C-F diff. > C-Cl diff
The Electronic Geometry is the resulting shape of the ________________________ that minimizes the repulsions between rheds
electrons
delocalized electrons
electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond. -appears in some resonance forms, but not others. Resonance form I contains 2 localized bonds and 1 delocalized bond. A delocalized charge is a formal charge that appears on one atom in some resonance forms and on other atoms in other forms.
Which elements can disobey the octet by having fewer than 8 e- surrounding it?
first five elements: H, He, Li, Be, and B
Amount of energy required to remove the first e- K(g) → K+(g) + e-
first ionization energy
______________________ __________________________ is a concept used to account for the distribution of electrons in a compound.
formal charge
Covalent bonds are formed between two _________________(metals or non-metals?)
formed between two non-metallic atoms
pairs of electrons that do not participate in bonding
lone pairs
The higher the electronegativity the _________________ the attraction the electrons have for that element.
greater
There are particular places on the periodic table where atoms have a finite electron affinity, and others where the EA is zero. These are places where adding another electron will give an atom an electron configuration that is either a filled subshell (or shell) or __________________________________ subshell.
half-filled
The size of an atom can be deduced experimentally by ______________ the distance between two atoms in a diatomic molecule.
halving
______________________ molecules are almost always polar. For example, CO has a small dipole moment, whereas HF has a much larger dipole moment. You should be able to prove that to yourself by looking at the differences in the electronegativity values.
heteronuclear molecules are almost always polar, but prove with diff. in electronegativity values
For liquids, higher IMFs usually means __________________ (higher or lower?) viscosity?
higher
It is important to note that each subsequent ionization energy is always________________than the previous one as we are reducing the number of electrons but the number of protons is fixed. Thus, as we remove electrons and decrease the shielding and repulsion, the effective nuclear charge is increasing.
higher
HOMO
highest occupied molecular orbital
_____________________________ diatomic molecules have no difference in electronegativity, therefore their dipole moment is zero (e.g. F2 and O2). In other words, they are nonpolar molecules.
homonuclear diatomic molecules have a dipole moment of zero and are nonpolar molecules
Only F, O, and N are the right size and have a high enough electronegativity to form _______________________bonds.
hydrogen
What is one way to tell if a bond is ionic?
if the molecule's formula is written out in words w/out charges explicitly listed. -ex. NaCl has the formula "sodium chloride"
Polarizability ______________________________ (increases or decreases?) with increasing # of electrons?
increases with incr. # of e- (ie. increasing sizes of molecules) -SO London forces are typ. stronger for molecules that have larger or more electrons
ionic solid
ion-ion interactions between the cations and anions -hard (bc ions are localized) -high melting point (higher than metallic but lower than covalent!) -conducts electricity in water (as a liquid bc the ions can move, but doesn't conduct electricity as a solid)
In general we can think about the formation of an______________bond as the sum of three processes. 1. The energy required to form the cation. 2. The energy that is gained by forming the anion. 3. The energy that is gained by bringing the cation and anion together.
ionic
Ionic bonds tend to be _______________ (more or less?) strong than covalent bonds bc of coulombic attractions between ions of opposite charges.
ionic bonds are typically MORE strong than covalent bonds!
___________________ bonds are chemical bonds in which we assume the electrons have fully "moved" from one element in the compound to another. As positively and negatively charged particles are attracted to one another, combinations of cations and anions form compounds that are held together by this electrostatic force. We refer to this as an _____________ _________________.
ionic, ionic bond
two elemental properties
ionization energy and electron affinity
smallest wavelength highest frequency highest energy (smallest or largest?) HOMO-LUMO gap
largest
MX(s) → M+ (g) + X- (g).
lattice energy
The energy that is gained by bringing the cation and anion together.
lattice energy
______________ _______________energy is directly proportional to the charges on the ions (higher charges result in higher_______________ _______________) and is inversely proportional to their sizes (smaller ions have higher ________________ ____________________).
lattice energy
A small plus sign is often drawn on the less electronegative end to indicate the partially positive end of the bond. The length of the arrow is proportional to the __________________________ of the electronegativity difference between the two atoms.
length of arrow is proportional to the magnitude of the electronegativity difference between the two atoms
Will H2+ be more or less stable than H2 and why?
less stable; H2+ has one less electron in bonding orbitals H2+ has 1 bonding electron and zero antibonding electrons. H2 has 2 bonding electrons and zero antibonding electrons. Higher bond orders indicate more stable molecules. Therefore, H2+ is less stable than H2 because it has one less bonding electrons.
2 bonds + 3 lone pairs =
linear
2 bonds + 4 lone pairs
linear
Ionic solid
metal and non-metal atoms
Metallic solid
metal atoms
metallic solid
metal atoms connected by dative bonds -malleable -delocalized electrons -thermal and electrical conductor
What is the strongest Intramolecular force?
metallic bonds: metal cations to delocalized electrons
Water molecules are often connected by strong hydrogen bonds. What type of solid would you expect ice to form?
molecular solid bc molecules are held together by IMFs
two additional things that Boiling Point depends on:
molecular weight and surface area!
The molecule AX5 has five RHEDs surrounding the central atom, A. Is this molecule polar?
no Each X atom is pulling the electrons away from the central atom equally. Since the molecule is trigonal bipyramidal, the five dipoles from the five bonds in the molecule are pointing in exactly opposite directions.
Is N-Cl a polar bond?
no bc both have nearly the same EN so EN diff. is basically zero
Should you include prefixes when writing out ionic compounds?
no, because w/ periodic table and knowledge of ionic bonding, we can determine the number of ions based on which elements are used
What causes irregular bond angles?
non-bonding electron pairs cause irregular bond angles -remember the "corralling kids" example
Molecular OR Covalent solids
non-metal atoms -Molecular solid usually melt below 500K -Covalent Network solids melt above 500K
Ionic compound will always contain at least one metal and non-metal or one __________________________________.
polyatomic ion
When shape is asked, refer to which geometry?
refer to the molecular geometry
Sometimes, when assembling a Lewis structure, one finds that a double bond can be placed in more than one location between two like atoms. When this situation occurs, it is usually an indication that the actual molecular structure is some average structure existing in some state between the available extremes. The average structure is said to exhibit _____________________, where experimental evidence supports this theory showing that the bonds that undergo_______________________each have a bond energy between the extreme (i.e., less than the strength of a double bond but greater than the strength of a single bond).
resonance
Ionization energy, atomic radius, and electron affinity are properties of a ________________ atom.
single
Cations have ________________ ionic radii than the corresponding anions.
smaller
If you have two ions with the same number of electrons, the ion with more protons will be ____________________.
smaller
The higher the bond energy, the 'stronger' we say the bond is between the two atoms, and the distance between them (bond length) is ____________________________ (smaller or larger?).
smaller
All linear molecules have bond angles of 180°. What is the hybridization of the central atom with 2 RHEDs in a linear molecule?
sp 2 RHEDs means we need 2 orbitals for bonding: 1 s orbital and 1 p orbital. Therefore, the hybridization of the central atom with 2 RHEDs in a linear molecule is sp.
4 bonds + 2 lone pairs
square planar
5 bonds + 1 lone pair
square pyramidal
What are all of the possible molecular geometries for a molecule with four RHEDs surrounding the central atom?
tetrahedral, trigonal pyramidal, and bent
When two orbitals combine in MO Theory, two new molecular orbitals are formed: one bonding orbital and one anti-bonding orbital. 1. The_____________________ orbital is ALWAYS lower in energy than the other orbital. 2. All anti-bonding orbitals are given the symbol, *
the BONDING orbital is always lower in energy than the nonbonding orbital!! -meaning the bonding orbital is more stable than the nonbonding orbital!
When two water molecules are interacting, what is true?
the covalent bond B (w/in each water molecule) is stronger than the hydrogen bond A (between the two water molecules)
The nuclear charge is of course the same for all of the electrons in an atom. However, we can understand from the previous unit that the valence electrons experience a different nuclear charge than the core electrons. What are periodic trends a direct result of?
the effective nuclear charge of an atom
Electron affinity
the energy released from an atom upon the addition of an electron to form the anion.
Ionization energy
the energy required to remove an electron from an atom in the gas phase.
lattice energy of an ionic compound
the energy required to separate one mole of the solid into its component gaseous ions.
cohesive forces
the forces of attraction between a liquid and itself
adhesive forces
the forces of attraction between two molecules
The magnitude of a bond dipole moment is represented by the Greek letter mu (µ), the magnitude of the partial charges as determined by the ___________________________ difference (Q), and the distance between the charges (r). µ = Qr
the magnitude of the partial charges is determined by the ELECTRONEGATIVITY difference (Q), and the distance between the charges (r).
An antibonding orbital is formed when...
the overlap of the corresponding atomic orbitals leads to destructive interference.
How do strength of intermolecular forces and vapor pressure relate?
the stronger the IMFs, the stronger the forces holding the molecules together, the LOWER the vapor pressure of a liquid at a given temperature -bc it is harder to vaporize a substance -To evaporate or change phase to a gas, liquids must overcome their IMFs. Therefore, substances with smaller IMFs tend to have higher vapor pressures.
boiling point
the temp at which IMFs break in order for a liquid to boil
The π bonding orbital has one node, whereas the π* anti-bonding orbital has __________ node(s).
two nodes (note that the picture is of only one node!)
How many unshared electrons and bonding electrons exist around the central atom in ozone (O3)?
two, six
We can use the ______________________ _________________________ and the corresponding effective nuclear charge of an atom to predict its relative size.
valence electrons
A dipole moment is often represented as a vector, where an arrow is drawn from the _________ electronegative atom toward the _________ electronegative atom.
vector arrow from less to more EN atom
Viscosity of gases __________________________(increases or decreases?) when the temperature increases?
viscosity of gases increases when the temperature increases bc the KE of gas molecules increases (more difficulty for gas molecules to pass through)
Viscosity of liquids ____________________ (increases or decreases?) when the temperature increases?
viscosity of liquids decreases when temp increases bc the IMFs between the molecules gets weaker
substance w/ high vapor pressures at normal temps is called
volatile!
Does volume of a container affect a liquid's vapor pressure?
volume of a container DOES NOT affect a liquid's vapor pressure bc -if volume is decreased, some of the vapor turns its a liquid state -if volume is increased, some of the liquid will change into its vapor state
In this case, the molecular structure is bent because of the lone pairs on oxygen, therefore the two bond moments do not cancel. Water does have a net dipole moment and ______(is/is not?) a polar molecule.
water is a polar molecule bc of its net dipole moment
Is the C-H bond polar or non-polar (pure)?
we will consider the C-H bond non-polar for this class because the EN difference is only 0.4
When do "permanent" dipoles occur?
when two different atoms have substantially different electronegativity
For the elements in the second period of the periodic table (principal energy level n=2), the s2p6 electrons comprise the octet, and no d sublevel exists. As a result, the second period elements (more specifically, the nonmetals C, N, O, F) obey the octet rule ___________________(how often?)___________.
without exception I.E. ALWAYS
Do molecules with the carboxyl (COOH) group exhibit hydrogen bonding?
yes, the O-H bond
