Chemistry: Ch 5

Which orbitals result in bond stabilization when they are occupied?

A bonding orbital is a molecular orbital located between two nuclei; electrons in a bonding orbital stabilize a molecule. An antibonding orbital is a molecular orbital located outside of the region between two nuclei; electrons in an antibonding orbital destabilize the molecule.

A molecular orbital is:

A wave-function occupied by a single electron in a molecule. Just like an atomic orbital describes the locations where electrons can be found in an atom, a molecular orbital describes a wave-function occupied by a single electron in a molecule.

What is the maximum bond order that is possible for a bond between elements in the first two rows of the periodic table?

3

What is the maximum bond order that is possible for a bond between elements in the second row of the periodic table?

3. No element in the second row can form more than a triple bond.

Four atomic orbitals will combine to give how many hybrid orbitals?

4

How many molecular orbitals will have an n value of 2?

8. The atomic orbitals with an n value of 2 are the 2s orbital and the three 2p orbitals. When these four orbitals from one atom interact with four orbitals from another atom, they generate 8 molecular orbitals, half of which will be bonding and the other half of which will be antibonding.

A sigma bonding orbital will result from p orbital overlap if:

Direct overlap generates sigma bonds, and the lobes must be in-phase to generate constructive interference and a bonding orbital.

How many electrons will be shown in the molecular orbitals section on the molecular orbital diagram for H2?

Each hydrogen atom will contribute one valence electron to the molecular orbital generated for a total of 2 electrons drawn in the section of the molecular orbital diagram that represents the molecular orbitals in an H2 molecule.

What is the highest occupied molecular orbital for Ne2?

Each neon atom has 8 valence electrons, so the 16 electrons total in the n=2 level will completely fill the n=2molecular orbitals as well. The σ∗2p orbital is the highest energy molecular orbital in Ne2, so it is the highest occupied molecular orbital. The π∗2p orbitals are also occupied, but they are lower in energy than the 2σ∗ orbital.

Which molecule will have a bond order of zero?

He2

In a sigma bond, the electron density is concentrated:

In a sigma bond, the electron density is located immediately upon the internuclear axis.

If an electron became excited, it could

Jump from the sigma (σs) or bonding orbital to the sigma star (σ∗s) or anti-bonding orbital. The sigma star antibonding orbital is higher energy, so if an electron becomes excited it will move from the sigma bonding orbital to the sigma star antibonding orbital.

Which molecule will have the same bond order as H2?

Li2

Which of the following is more accurate in determining bond order?

Molecular orbital theory. Molecular orbital theory is more accurate in determining bond order than Lewis structures. MO theory describes the structure and the geometry of the molecule more in depth by taking into consideration the overlap and energies of the bonding and antibonding electrons residing in a particular molecular orbital.

Which of the following molecules has a nitrogen atom with an sp2 hybridization?

NO3-

Which of the following determines the strength of a covalent bond?

The amount of overlap for the orbitals involved. When overlap occurs between two atomic orbitals, the positively charged nuclei and the negatively charged electrons for the atoms involved create a covalent bond. The more overlap that occurs between two orbitals, the stronger the attraction between the positively charged nuclei and the negatively charged electrons. Therefore, the more overlap that occurs, the stronger the covalent bond.

According to molecular orbital theory, the regions of the wave function with the highest probability of finding electrons are areas with _______.

Constructive interference. The wave function ψ is used in molecular orbital theory to describe the behavior of electrons in a molecule. We use LCAO to combine the wave functions of atomic orbitals to generate molecular orbitals. Combination of in-phase waves produces constructive interference, generating a wave with a greater amplitude and a higher probability of electron density. Combination of out-of-phase waves produces destructive interference, and describes areas with a low probability of electron density.

When atomic orbitals of two nuclei overlap, the mutual attraction between a negatively charged electron pair and the two positively charged nuclei forms:

Covalent bond. When overlap occurs between two atomic orbitals, the positively charged nuclei and the negatively charged electrons that form a pair create a physical bond that is the covalent bond. The more overlap that occurs between two orbitals, the stronger the attraction between the positively charged nuclei and the negatively charged electrons.

Hybrid orbitals can contain what?

bonding valence electrons

A pi bond involves what?

lateral orbital overlap, a node. Pi bonds involve the lateral overlap of p orbitals, in which the electron density is on either side of the internuclear axis. Along the axis, there is a node in which there is no probability of finding an electron.

The energy of an sp orbital will be:

less than that of a p orbital but greater than that of an s orbital

When two atomic orbitals combine, they will generate:

one bonding orbital and one antibonding orbital

In order for pi bonds to form, there must be:

overlap of unhybridized orbitals

Based on bond order, which of the following can exist?

C2. Using the bond order formula (bonding−nonbonding2) we can determine that Be2 will have a bond order of 0(4−42=0) and Ne2 will have a bond order of 0(10−102=0). Because their bond orders are 0, the molecules will not exist. C2 will have a bond order of 2(8−42=2).

Hybridization predicts geometry best for:

small atoms

What is the hybridization of C in CN−?

sp orbital

Hybridization was developed to explain observations about:

the bond angles in certain molecules

When out-of-phase atomic orbitals combine, they create:

Antibonding molecular orbitals

Bond order allows us to identify:

Bond order allows us to identify the net number of electron pairs participating in bonding interactions between two atoms. We can determine the bond order of a molecule by subtracting the antibonding (destablizing electrons) from the bonding (stabilizing electrons) and dividing this number by two. The larger the bond order, the stronger the bond between the two given atoms. The bond order is the number of bonding pairs of electrons between two atoms, when using Lewis structures.

Which molecule has a central atom that is sp3d hybridized? CF4 BrF3 ClF5 NH3

BrF3. With two lone pairs and three single bonds, bromine has five electron domains which will make it sp3d hybridized.

Which phenomenon that goes unexplained by Lewis structures is solved by applying molecular orbital theory?

The paramagnetism of the oxygen molecule. Lewis structures would show oxygen as having all paired electrons, but it exhibits paramagnetism, which requires unpaired electrons. This issue is solved by applying molecular orbital theory.

Which kind of orbitals can s orbitals overlap with?

The s orbitals can overlap with any of the sp , sp2 , and sp3 hybridized orbitals to form covalent bonds.

The image provided shows two 3py orbitals. Predict what type of molecular orbital will result.

The side by side overlap of the two 3p orbitals will result in the formation of a π3py bonding orbital because they are in-phase.

Which bond is the shortest?

Triple bonds.

What can be used to determine the hybridization of central atoms?

VSEPR Theory. VSEPR theory can be used to determine the hybridization of central atoms because of its ability to predict electron pair geometries. These geometries are dependent on the number of electron dense regions around a central atom. Single bonds, multiple bonds, radicals, and lone pairs each count as one electron dense region.

Which molecule has a central atom that is sp3d2 hybridized? XeF2 XeF4 XeF6 None of the above

XeF4. Only XeF4 will have six electron domains, in the form of four bonds and two lone pairs, so it will be sp3d2 hybridized.

How many electrons will be shown in the molecular orbitals section on the molecular orbital diagram for O2?

Each oxygen atom will contribute eight electrons to the molecular orbitals generated for a total of 16 electrons drawn in the section of the molecular orbital diagram that represents the molecular orbitals in an O2 molecule.

A pi antibonding orbital will result from a p orbital overlap if:

Lateral overlap generates pi bonds, and the lobes must be of opposite phase to generate destructive interference and an antibonding orbital.

When the lobes of two p orbitals are in the same phase and overlap side-by-side, the orbital that is formed has a _____ dissociation energy compared to the σ∗ molecular orbital formed from the out-of-phase direct overlap of the two p orbitals.

Lower. The in-phase side-by-side overlap of two p orbitals will generate the π bonding molecular orbital while the out-of-phase direct overlap of two p orbitals will generate the σ∗ antibonding molecular orbital. For the molecular orbitals that are formed from the p orbitals in the same shell, the bonding molecular orbitals will have a lower dissociation energies compared to the antibonding molecular orbitals.

Which of the following molecules contains an occupied orbital with a node, or nodal plane, along the internuclear axis? O2, H2, N2, HCl, or HBr

O2 and N2. In a π bond, the regions of orbital overlap lie on opposite sides of the internuclear axis. Along the axis itself, there is a node: a plane in which there is no probability of finding an electron. Of the molecules listed above, only O2 and N2 will contain π bonds, and so only O2 and N2 will contain a node along the internuclear axis.

A _____ bond is a covalent bond where the regions of orbital overlap are above and below the internuclear axis.

Pi bond. Pi (π) bonds form on opposite sides of the internuclear axis (above and below the axis), creating a node along the axis. πbonds form from lateral overlap of p orbitals.

Unhybridized orbitals overlap to create:

Pi bonds

A pi bond involves:

π bonds involve side-by-side or lateral orbital overlap, in which the electron density is on either side of the internuclear axis. Along the axis itself, there is a node: a plane in which there is no probability of finding an electron.

When s−p mixing occurs, which type of orbitals reverse in the order of being filled?

σ2p bonding and π2p bonding. The sigma and pi orbitals will switch order for the 2p molecular orbitals.