smartbook 14

the valence molecular orbital diagram for the anion B2- is given. which of the following options correctly interpret this diagram?

-B2- is paramagnetic -the molecular orbital bond order is equal to 3/2 -B2- has a shorter bond than B2

which of the following statements are consistent with the molecular orbital description of the bonding in the O2 molecule?

-O2 is paramagnetic -O2 is more reactive than N2 -the bond order is equal to 2

which of the following statements correctly describe the rules used for placing electrons in molecular orbitals?

-lower energy orbitals are filled before placing electrons in higher energy orbtials -if two MOs have equal energy, an electron must be placed in each orbital before pairing up -orbitals are filled in order of increasing energy

why is the hybridization model necessary to explain the bonding in a molecule such as CH4?

-the atomic electron configuration of carbon cannot account for four equivalent bonds -the observed bond angles cannot be explained with reference to unhybridization orbitals

molecular orbital theory

a molecule is seen as a collection of nuclei with orbtials delocalized over the whole molecule

sigma bond

allows free rotation about the bond axis

hybrid orbitals are formed by the combination or "mixing" of ______ orbitals from a specific atom. the number of hybrid orbitals formed is ______ to/than the number of orbitals mixed, and the _____ of hybrid orbital varies according to the specific orbitals mixed

atomic ; equal ; type

valence bond theory

atoms are bonded through localized overlap of half-filled, hybridized, valence shell atomic orbitals

the molecular orbital bond order is calculated as 1/2[x-y] where x is the number of electrons in ______ molecular orbitals and y is the number of electrons in ____ molecular orbitals. in general, the higher the molecular orbital bond order, the _____ the bond strength for the species

bonding ; antibonding ; greater

valence bond theory proposes that before a covalent bond forms, atomic orbitals from a given atom can combine to form new atomic orbitals. this process is called ________ of orbitals, and the new atomic orbitals are referred to as ____ orbitals

hybridization ; hybrid

a double bond is ____ a single bond because the strength of the pie bond component is ___________ that of the sigman bond component

less than twice as strong as; weaker than

sp

linear

a molecular orbital is a region of space in a covalent species where electrons are likely to be found. the combination of two atomic orbitals always forms two molecular orbitals; the bonding molecular orbital, which is _______ in energy, and the antibonding molecular orbital, which is _____ in energy, than the original atomic orbitals

lower ; higher

in a polar covalent bond, the bonding MOs will be closer in energy to the AOs of the ___ electronegative atom

more

atomic orbitals that are not involved in bonding are called _________ MOs. these MOs will have ______ energy as/to the isolated atomic orbitals

nonbonding ; the same

sp3d2

octahedral

a double bond acts as ___ electron group(s) even though there is/are ___ electron pair(s) shared between the bonding atoms. this is because each electron pair occupies a different orbital, which reduces ______ between them. similarly the three bonds of a triple bond form ____ group(s)

one ; two ; repulsion ; one

which of the following statements correctly defines hybrid orbitals?

orbitals used for bonding that are formed by mixing atomic orbitals from the same atom

a molecular species with one or more unpaired electrons in an MO is _____ and will be attracted to a magnetic field, whereas a species with no unpaired electrons in its MO is ______ and will be slightly repelled by a magnetic field

paramagnetic ; diamagnetic

pie bond

restricts rotation about the bond axis

o2p

single region of high electron density between bonded nuclei

the combination of one s and two p orbitals will form a group of three ____ hybrid orbitals. these hybrid orbitals adopt a(n) ______ planar geometry and are at an angle of ____ to the remaining unhybridized p orbital

sp2 ; trigonal ; 90

sp3

tetrahedral

why do the energies of the molecular orbitals formed for species of O2, F2 and Ne2 differ from those of the molecular orbitals for other period 2 elements?

there is a large energy difference between the 2s and 2p orbitals of O, F and Ne; therefore, no s-p mixing occurs when molecular orbitals are formed

sp3d

trigonal bipyramidal

sp2

trigonal planar

which of the following is the correct molecular electron configuration of O2+, including electrons from valence atomic orbitals only?

(sigma2s)^2(sigma*2s)^2(sigma2p)^2(pie2p)^4(pie*2p)^1

which of the following statements correctly describe valence bond theory?

-a shared electron pair has the highest probability of being located between the nuclei of the bonded atoms -the extent of orbital overlap depends on the shape and direction of the orbitals involved -the space formed by overlapping orbitals can accommodate a maximum of two electrons

which of the following statements correctly describe a sigma bond?

-a sigma bond results from end-to-end overlap of two orbitals -single bonds are sigma bonds

consider the combination of two atomic orbitals to form a pair of molecular orbitals, designated o2s and o*2s. which of the following statements explain these designation correctly?

-both orbtials are designated sigma because they are cylindrically symmetrical -the atomic orbitals that combine in this case are s orbitals

hybridization is less useful as a bonding model when describing the bonding in _____

-large nonmetal hybrides -structures with expanded valence shells

which of the following statements correctly describe a covalent bond in terms of valence bond theory?

-the greater the overlapped area, the stronger the bond -the electrons of a shared pair must have opposite spins -a covalent bond is formed by the overlap of an orbital from each of the bonding atoms

which of the following statements correctly describe molecular orbital bond orders?

-the lower the molecular orbital bond order, the weaker the bonds between the atoms of the species -a species with more electrons in bonding than antibonding molecular orbitals will have a positive molecular orbital bond order

which of the following options correctly describe the C=N double bond in the structure shown?

-the pie bond on the C=N bond is formed by sideways overlap of a p orbital from each atom -the sigma bond is formed by the end-to-end overlap of an sp2 orbital from each atom

which of the following statements correctly describe hybrid orbitals?

-the spatial orientations of the hybrid orbitals match observed molecular shapes -the shape and orientation of a hybrid orbital allow maximum overlap with an orbital from another atom to form a bond -the type of hybrid orbital formed varies depending on the specific combination of atomic orbitals

the MO diagram for the hydroxide ion, -OH is shown. select all the statements that correctly interpret this diagram

-there are 3 nonbonding MOs in this species -the MO bond order is given by 2/2 = 1 -the -OH is a fairly stable species

a triple bond is composed of ___ sigma and ___ pie bond(s)

1 ; 2

a double bond is always made up of ___ sigma and _____ pie bonds. a double bond is _____ than a single bond

1 ;1 ; stronger

arrange the steps for determining the hybridization of an atom in the correct order.

1.) draw a lewis structure using the molecular formulas 2.) count the number of electron groups surrounding the center atom 3.) the number of hybrid orbitals required is equal to the number of electron groups 4.) build the appropriate combination of atomic orbitals based on the number of bonding orbitals required

place the following molecular orbitals in order of decreasing energy for species of B2, C2, and N2. start with the highest energy orbital at the top of the list.

1.) o*2p 2.) pie *2p 3.) o2p 4.) pie2p

place the following molecular orbitals in order of decreasing energy for species of O2, F2, and Ne2. start with the highest energy molecular orbital at the top of the list.

1.) o*2p 2.) pie*2p 3.) pie2p 4.) o2p

o2p orbital

formed by end-to-end combination of atomic 2p orbitals

pie 2p orbitals

formed by side-to-side combination of atomic 2p orbitals

hybrid orbitals are designated by using a superscript to indicate the ____ of each type of orbital used to form them. for example, the designation sp2 indicates that _____ s and ____ p orbital(s) were combined to form this orbital type

number ; one ; two

the hybridization of one s and one p orbital will result in the formation of two ___ hybrid orbitals. this will leave ___ unhybridized valence p orbital(s), lying at right angles to the hybrid orbitals

sp ; two

pie2p

two separate regions of high electron density between nuclei, above and below bond axis

according to the molecular orbital model of covalent bonding, orbitals are viewed as ____ functions. the formation of a bond involves the mathematical combination of these functions, either by _________ to give an area of increased electron density, or by ______ to give an area of decreased electron density

wave ; addition ; subtraction

the lower the molecular orbital bond order, the _____ the bond and the ____ stable the species

weaker ; less

when should the VSEPR model and hybridization theory to be applied to describe bonding?

whenever an observed molecular shape needs to be rationalized in terms of atomic orbitals

o*2p and pie*2p

zero electron density between bonded nuclei

which of the following statements correctly describe sp3 hybrid orbitals?

-the four sp3 hybrid orbitals of a group are equivalent in shape and energy -an sp3 hybrid orbital is unsymmetrical in shape, having one small and one large lobe

which of the following statements correctly describe bonding and antibonding molecular orbitals?

-a bonding molecular orbital is lower in energy than the original atomic orbitals -a bonding molecular orbital is formed by the addition of the wave functions for two atomic orbitals -an antibonding molecular orbital has a region of zero electron density between the nuclei of the bonding atoms

which of the following statements correctly describe a pie bond?

-a multiple bond always contains at least one pie bond -a pie bond is formed by the side to side overlap of two p orbitals

molecular orbitals can be formed by the combination of multiple atomic orbitals, allowing electrons to be _______ or shared between several atoms. the molecular orbital model therefore allows a better description of the bonding in _______ structure than valence bond theory, which depicts electrons as being ______ between two atoms at a time

delocalized ; resonance ; localized

a central atom can be surrounded by five or six electron groups if ___ orbitals are available for bonding. the appropriate number of equivalent bonding orbitals is formed by combining ___ s orbital(s), ___ p orbital(s), and one or two __ orbitals

d ; one ; three ; d