Chapter 3: Bonding and Chemical Interactions Flashcards
Which element?
____________ can only have 2 valence electrons.
Hydrogen
Which elements?
________ and ____________ bond to attain 2 and 4 valence electrons, respectively.
Lithium and beryllium
Which element?
________ bonds to attain 6 valence electrons.
Boron
All elements in period ____ and greater can expand the valence shell to include more than 8 electrons by incorporating the ____-orbitals.
3; d
An ________________ octet can occur in elements that are stable with fewer than 8 electrons in their valence shell, and include hydrogen (2), helium (2), lithium (2), beryllium (4), and boron (6).
incomplete
An ________________ octet can occur in any element in period 3 and greater; they can hold more than 8 electrons. This includes phosphorus (10), sulfur (12), chlorine (14), and many others.
expanded
Any molecules with an odd number of valence electrons (can/cannot?) distribute those electrons to give 8 to each atom - cannot achieve the octet rule.
cannot
Which 6 elements almost always abide the octet rule?
- carbon
- nitrogen
- oxygen
- fluorine
- sodium
- magnesium
In ________ bonding, 1+ electrons from a low IE element are transferred to an atom with high electron affinity.
typically metal to nonmetal
ionic
What holds ionic bonds together? This type of attraction creates ________ structures consisting of repeating rows of cations and anions, rather than individual molecular bonds.
The electrostatic attraction between opposite charges; lattice
In ____________ bonding, an electron pair is shared between 2 atoms, typically nonmetals, that have similar values of electronegativity.
covalent
The degree to which the pair of e- is shared (un)equally between 2 atoms determines the degree of ____________.
polarity
If the e- pair is shared equally, the bond is ____________. If unequally, the bond is ________. If both of the shared electrons are contributed by only one of the 2 atoms, the bond is called ________________ ____________.
nonpolar; polar; coordinate covalent
Unlike ionic crystal lattices, covalent compounds consist of what?
Individually bonded molecules
________ bonds form between atoms that have significantly different electronegativies.
ionic
Atoms that lose electrons are ________, atoms that gain electrons are ________.
cations; anions
Electrons are not ________ in an ionic bond, but rather ________________.
shared; transferred
What value?
For electron transfer to occur, the difference in electronegativity should be greater than ____ on the Pauling scale.
1.7
Because of the strength of electrostatic forces between constituents of ionic compounds, they have (low/high?) melting and boiling points.
very high
Ionic compounds also ________ in water and other polar solvents, and are good ____________ of electricity in the molten or aqueous state.
dissolve; conductors
In an ionic lattice structure, the attractive forces between oppositely charged ions are ____________ and repulsive forces between ions of like charge are ____________.
maximized, minimized
When 2+ atoms with similar ________________ interact, energy required to form ions through the complete transfer of 1+ electrons is greater than the energy that would be released upon formation of an ionic bond.
electronegativities
instead, they share electrons
i.e. 2 atoms of similar tendency would not form an ionic compound because it is energetically unfavorabel
Covalent compounds contain discrete molecular units with relatively (weak/strong?) intermolecular forces.
weak
The number of shared electron pairs between 2 atoms is called the ________ ________.
bond order
single bond = order of 1
double bond = 2
triple bond = 3
________ ________ is the average distance between 2 nuclei of atoms in a bond.
bond length
As the # of shared e- pairs increases, what happens to bond length?
The 2 atoms are pulled closer together and bond length decreases
________ ________ is the energy required to break a bond by separating its components into their isolated, gaseous atomic states.
bond energy
The greater the # of pairs of e- shared between atomic nuclei, the (less/more?) energy is required to break these bonds.
more
The greater the bond energy, the (weaker/stronger?) the bond.
stronger
____________ occurs when 2 atoms have a relative difference in electronegativities. The atom with higher EN gets the larger share of e- density.
polarity
A polar bond creates a ________, with the positive end at the less EN atom and the negative end at the more EN atom.
partial charges!!
dipole
When atoms have (nearly) identical EN, they get an equal distribution of e-. This is a ____________ ____________ bond.
nonpolar covalent
no separtion of charge
What are the 7 common diatomic molecules?
- H2
- N2
- O2
- F2
- Cl2
- Br2
- I2
What value?
Any bond between atoms with a difference in EN less than ____ is generally considered nonpolar.
0.5
Atoms that differ moderately in their electronegativities will share e- unevenly, creating ________ ________________ bonds.
polar covalent
The difference in EN should be between ____ and ____.
0.5 and 1.7
Polar covalent bonds don’t form ionic bonds, but due cause a ________________ of charge across the bond.
separation
The ____________ ____________ of the polar bond or polar molecule is a vector quantity.
dipole moment
The vector quantity of a polar bond is given by what equation? What does each qty stand for?
p = qd
p = dipole moment
q = magnitude of charge
d = displacement
Equation 3.1
The dipole moment vector, represented by an arrow pointing from the positive to negative charge, is measured in ____________ ________. What is it?
Debye units - coulomb meters
In a ________________ ____________ bond, both shared electrons originated on the same atom. This means that a lone pair of one atom attacked another atom with an unhybridized p-orbital to form a bond.
coordinate covalent
Coordinate covalent bonds are typically found in ________ ____-____ reactions.
Lewis acid-base
A Lewis acid is any compound that ________________.
accepts a lone pair of e-
A Lewis base is any compound that ________________.
donates a pair of e-
The electrons involved in a covalent bond in the valence shell are ____________ electrons. Those not involve are ________________ electrons.
bonding; nonbonding
The unshared e- pairs are known as ________ pairs, because they are associated with only one atomic nucleus.
lone
Formal charge is what? How is it calculated?
The charge assigned to an atom or molecule
It is calculated by the number of valence electrons minus the number of nonbonding valence electrons minus 1/2 the total number of electrons shared in bonds
Formal charge = valence electrons - dots - sticks
________ structures represent how the electrons are arranged around individual atoms in a molecule.
Lewis
The arrangement that ________________ the # and magnitude of formal charges is usually the most stable arrangement of the compound.
minimizes
Each dot on a Lewis dot diagram represents what?
an s or p valence electron of an atom
For Lewis structures, the least ____________________ atom is the central atom.
electronegative
Formal charge ____________ the effect of EN difference, and oxidation numbers ____________ the effect of EN difference.
underestimate; overestimate
in oxidation state, we assume the more EN atom has 100% of the bonding e- share
It may be possible to draw 2+ Lewis structures that demonstrate the same arrangement of atoms but that differ in the specific placement of electrons. These are ____________ ____________, and are represented with a double-headed arrow.
resonance structures
The more stable a resonance structure is, the more it contributes to the ________________ of the resonance hybrid.
character
A Lewis structure with ________ or ____ formal charges is preferred over one with large formal charges.
small/ no
A Lewis structure with ____ separation between opposite charges is preferred
less
A Lewis structure where negative formal charges are placed on ____ EN atoms is more stable.
more
____________ geometry describes the spatial arrangement of all pairs of electrons around the central atom, including both bonding and lone pairs.
Electronic
most important for ideal bond angle
____________ geometry describes the spatial arrangement of only the bonding pairs of electrons.
Molecular
main focus of MCAT
The ________________ number, which is the # of atoms that surround and are bonded to a central atom, is the relevant factor when determining molecular geometry.
coordination
Nonbonding pairs are exert (more/less?) repulsion than bonding pairs because these electrons reside closer to the nucleus.
more
A compound with nonpolar bonds is always ________.
nonpolar
If the compound has a molecular geometry such that the bond dipole moments cancel each other out, then the result is a ____________ compound.
nonpolar
usually symmetrical
When 2 atoms bond to form a compound, the atomic orbitals interact to form a ________________ orbital that describes the probability of finding the bonding electrons in a given space.
molecular
Molecular orbitals are obtained by combining the ________ ____________ of the atomic orbitals.
wave functions
If the signs of the 2 atomic orbitals are the same, a ____________ orbital forms. If different, an ________________ orbital forms.
bonding; antibonding
When orbitals overlap head-to-head, the resulting bond is a ________ bond. These allow for free rotation because the e- density of the bonding orbital is a single linear accumulation between atomic nuclei.
sigma
When orbitals overlap to form 2 parallel e- cloud densities, a ____ bond is formed. They do not allow for free rotation because the e- densities are parallel and cannot be twisted.
pi
Atoms and compounds can participate in weak electrostatic interactions. What are the 3 types of intermolecular forces (IMFs)?
- London dispersion forces
- dipole-dipole interactions
- hydrogen bond
The weakest of intermolecular interactions are the dispersion forces, known as ________ forces.
London
Electron density is unequally distributed between 2 atoms in any given moment, resulting in rapid polarization and counterpolarization of the e- cloud and the formation of short-lived dipole moments. These dipoles are generated with neighboring molecules as well. What type of IMF is this?
London dispersion forces
weakest because they shift constantly
The next weakest after London forces are ________-________ interactions, which are of intermediate strength.
dipole-dipole
Polar molecules tend to orient themselves so that the oppositely charged ends of the respective molecular dipoles are closest to each other: the positive region of one molecule is close to the negative region of another molecules. Denoted by dashed lines. What IMF is this?
dipole-dipole interactions
present in solids and liquids, not gas (too far apart)
Polar species tend to have (lower/higher?) melting and boiling points because of dipole-dipole interactions.
higher
Finally, the strongest type of interaction is the ____________ bond.
hydrogen
not actually a bond - no sharing or transfer of e-
Hydrogen bonds are an unusually strong form of ________-________ interaction that can be ________- or ____________. What types of molecules is it common to see this?
dipole-dipole; intra or intermolecular
Common in biochemical molecules, especially water!
When hydrogen is bonded to 1 of 3 highly EN atoms, the H atom carries only a small amount of e- density in the covalent bond. What 3 atoms?
Hydrogen bonds, pick up the FON (phone)
Fluorine, oxygen, nitrogen
Hydrogen bonds
The positively charged hydrogen atom interacts with the partial negative charge of fluorine, oxygen, or nitrogen on nearby molecules. The H atom acts like a naked ________
proton
Substances that display hydrogen bonding tend to have unusually (low/high?) boiling points compared to compounds of similar molecular weights that do not exhibit H bonding.
high
