Ch 11

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

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

no unpaired electrons present

diamagnetic

Single region of high electron density between bonded nuclei

sigma 2p

allows free rotation about the bond axis

sigma bond

Zero electron density between bonded nuclei

sigma*2p and pi*2p

Molecular Orbital theory

A molecule is seen as a collection of nuclei with orbitals dlocalized over the whole molecule

Valence Bond theory

Atoms are bonded trhough localized overlap of half filled, hybridized, valence-shell atomic orbitals

The boron atom in the structure shown requires 3 equivalent bonding orbitals, which are formed by combining ______ s and _______ p orbitals from the boron atom to form 3 equivalent ________ hybird orbitals. There is _____ unhybridized p orbitals on the boron atom which contains no electrons.

one, two, sp2, 1

A group of sp3 hybrid orbitals is formed by the hybridization of ________s and _______ p orbitals from the valence shell of an atom. These hybrid orbitals have the same ___________ and energy.

one; three; shape

Which of the following statements correctly defines hybrid orbitals?

orbitals formed by mixing atomic orbitals from two different atoms in certain order

one or more unpaired electrons present

paramagnetic

restricts rotation about the bond axis

pi bond

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

pi2p

A bond formed by sideways overlap of 2 p orbitals (one from each bonding atom) is called a(n) ___ bond. This type of bond has ______ regions of electron density

pi; 2

Molecular orbitals formed from the combination of atomic s orbitals are called ________ molecular orbitals because they are cylindrically symmetrical. The molecular orbitals formed from atomic orbitals are designated sigma * 1s for the ____ molecular orbital and sigma 1s for the ________ molecular orbital.

sigma, antibonding, bonding

In a polar covalent bond, the bonding Mos will be closer in energy to the AOs of the _____________ electronegative atom.

more

Which of the following correctly describe bonding and antibonding molecular orbitals?

- a bonding molecular orbital is lower in energy than the original atomic orbital -An antibonding molecular orbital has a region of zero electron density between the nuclei of the bonding atoms - a bonding molecular orbital is formed by addition of the wave functions for the 2 atomic orbitals

Which of the following options correctly describe an MO energy-level diagram?

- the MO diagram shows the relative energy and number of electrons in each MO - The MO diagram can be used to calculate bond order and predict stability - the MO diagram typically includes valence-shell molecular orbitals only

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

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

Which of following statements correctly describe a sigma bond?

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

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

1 sigma and 2 pi bonds

A double bond acts as ___________ electron group (s) even though there is/ are _______ electron pair(s) shared between the bonding atoms. This is because every electron pair occupies a different orbital, which reduces ________ between them. Similarily the three bonds of a triple bond form _____ group(s)

1,2, repulsions, one

The valence molecular orbital diagram for Li2- is shown. The molecular orbital bond order for this species is equal to ____ and Li2- is _______stable than Li2

1/2 ; less

which of the following is the correct equation for calculating molecular orbital bond order?

1/2 [(# of e- in bonding MO) - (# of e- in antibonding MO)]

A double bond is always made up of ____ sigma and ____ pi bonds. A double bond is _____ than a single bond

1;1; stronger

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 orbitals varies according to the specific orbitals mixed.

atomic, equal, number

Hybrid orbitals are designated by using a superscript to indicate the ___ of each type of orbital used to form them. For example, the designation of sp2 indicateds that _____ s and ______ p orbitals were combined to form this orbital type.

number; one; two

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 ______ structures than VB theory, which depicts electrons as being ______ between two atoms at a time.

delocalized; resonance; localized

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 orbitals -orbitals are filled in order of increasing energy. -If two MOs have equal energy, an electron must be placed in each orbital

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, whihc is __ in energy, and the antibonding molecular orbital, which is ___________ in energy than the original atomic orbitals.

lower; higher