Question 1

According to valence bond theory, the triple bond in ethyne (acetylene, C₂H₂) consists of

Accepted Answer

The answer of According to valence bond theory, the triple...

Question 2

According to molecular orbital theory, what is the bond order in the O₂⁺ ion?

Accepted Answer

The answer of According to molecular orbital theory, what is...

Question 3

Determine the shape (geometry) of PCl₃ and then decide on the appropriate hybridization of phosphorus in this molecule. (Phosphorus is the central atom.)

Accepted Answer

The molecule PCl5 has phosphorus as the central atom with five bonding regions and no lone pairs, leading to a trigonal bipyramidal shape. This geometry corresponds to sp^3d hybridization.

Question 4

Overlap of two sp² hybrid orbitals produces a bond.

Accepted Answer

This statement is false. The overlap of two sp² hybrid orbitals would produce a sigma bond, not a bond labeled with a specific alphanumeric identifier.

Question 5

The angles between sp² hybrid orbitals are 109.5°.

Accepted Answer

The angles between sp^3 hybrid orbitals are 109.5°, not sp hybrid orbitals.

Question 6

Which of the following statements relating to molecular orbital (MO) theory is incorrect?

Accepted Answer

This statement is incorrect because in molecular orbital theory, stable molecules with an even number of electrons can have unpaired electrons in degenerate orbitals. This is known as Hund's rule.

Question 7

The nitrosonium ion, NO⁺, forms a number of interesting complexes with nickel, cobalt, and iron. According to molecular orbital theory, which of the following statements about NO⁺ is correct?

Accepted Answer

The answer of The nitrosonium ion, NO⁺, forms a number...

Question 8

Hybrid orbitals of the sp³d type occur in sets of four.

Accepted Answer

Hybrid orbitals of the type described (sp^3d) occur in sets of five, not four, as they involve the mixing of one s orbital, three p orbitals, and one d orbital.

Question 9

According to valence bond theory, overlap of bonding orbitals of atoms will weaken a bond, due to electron-electron repulsion.

Accepted Answer

According to valence bond theory, overlap of bonding orbitals of atoms will strengthen a bond by promoting the formation of a shared electron pair between the atoms. Weakness or strength of a bond is not determined by electron-electron repulsion.

Question 10

In the valence bond treatment, overlap of an s orbital on one atom with an sp³ orbital on another atom can give rise to a σ bond.

Accepted Answer

Overlap of an s orbital on one atom with an sp orbital on another atom can give rise to a sigma bond.

Question 11

Which one, if any, of the following statements about the MO treatment of the bonding in benzene is correct?

Accepted Answer

According to MO theory, the lowest energy pi-bonding MO in benzene has two hexagonal lobes, above and below the plane of the carbon atoms. This is known as the π bonding MO and can hold up to 6 electrons (3 pairs of electrons). The other statements are not correct: A) MO theory does not rely on resonance to explain the delocalized nature of the bonding in benzene. B) The lowest energy pi-bonding MO can only hold 6 electrons, not any more. C) MO theory predicts that benzene should be diamagnetic, not paramagnetic.

Question 12

Atoms of period 3 and beyond can undergo sp³d² hybridization, but atoms of period 2 cannot.

Accepted Answer

This is because hybridization requires the participation of atomic orbitals, and elements in period 2 do not have enough empty atomic orbitals to participate in this type of hybridization.

Question 13

A carbon-carbon double bond in a molecule may give rise to the existence of cis and trans isomers.

Accepted Answer

A carbon-carbon double bond restricts rotation around the bond, leading to two possible arrangements of the atoms around the bond. In the cis arrangement, the two substituents are on the same side of the double bond, while in the trans arrangement, they are on opposite sides. Therefore, the double bond in a molecule may give rise to cis and trans isomers.

Question 14

Select the correct statement about  -bonds in valence bond theory.

Accepted Answer

The answer of Select the correct statement about  -bonds...

Question 15

According to the molecular orbital (MO) treatment of the NO molecule, what are the bond order and the number of unpaired electrons, respectively?

Accepted Answer

The molecular orbital (MO) theory for the NO molecule indicates a bond order of 2.5, which is calculated by subtracting the number of electrons in antibonding orbitals from the number of electrons in bonding orbitals and then dividing by 2. NO has 11 valence electrons, and when these are placed in the molecular orbitals according to the MO theory, it results in a bond order of 2.5. Additionally, there is 1 unpaired electron in the molecular orbital configuration of NO, making it paramagnetic.

Question 16

One can safely assume that the 3s- and 3p-orbitals will form molecular orbitals similar to those formed when 2s- and 2p-orbitals interact. According to molecular orbital theory, what will be the bond order for the Cl₂⁺ ion?

Accepted Answer

Bond order is calculated as (number of bonding electrons - number of anti-bonding electrons) / 2. Using molecular orbital theory, we can construct the molecular orbital diagram for the Cl₂⁺ ion. The 2s and 2p orbitals of each atom will combine to form molecular orbitals, with the 2s contributing to the lower-energy bonding orbitals and the 2p orbitals contributing to the higher-energy anti-bonding orbitals. The 3s and 3p orbitals will also form molecular orbitals, with the 3s orbitals contributing to the lower-energy bonding orbitals and the 3p orbitals contributing to the higher-energy anti-bonding orbitals. The bonding electrons in this ion will occupy the Cl₂^{molecular orbital, while the anti-bonding electrons will occupy the Cl₂} molecular orbital. Counting the number of bonding electrons and anti-bonding electrons, we get a bond order of (2-1)/2 = 0.5 for the Cl₂⁺ ion.

Question 17

How many sigma and pi bonds, respectively, are in the molecule below? CH₃CH₂CHCHCH₃?

Accepted Answer

The answer of How many sigma and pi bonds, respectively,...

Question 18

Valence bond theory explains the bonding in diatomic molecules such as HCl without resorting to the use of hybrid orbitals.

Accepted Answer

Valence bond theory explains bonding in terms of the overlap of atomic orbitals, without needing to invoke the concept of hybrid orbitals.

Question 19

According to molecular orbital (MO) theory, the twelve outermost electrons in the O₂ molecule are distributed as follows:

Accepted Answer

According to the molecular orbital theory, the molecular orbitals for the O₂ molecule are formed by the combination of the atomic orbitals of the constituent atoms. The 12 outermost electrons will fill the molecular orbitals in a similar manner to the filling of atomic orbitals. The highest energy molecular orbital is the antibonding π2px orbital. This is followed by the antibonding π*2p y and π*2pz orbitals. The π2py and π2pz orbitals are both nonbonding orbitals. The remaining molecular orbitals are all bonding orbitals. There are four molecular orbitals that are completely filled by the 12 outermost electrons; these are the σ2 s, σ*2s, σ2pz, and σ*2pz orbitals. There are two partially filled molecular orbitals; these are the σ2px and σ*2px orbitals. Therefore, there are a total of 8 bonding MOs and 4 antibonding MOs, making the correct answer D.

Question 20

In the valence bond treatment, a  bond is formed when two 2p orbitals overlap side to side.

Accepted Answer

The answer of In the valence bond treatment, a ...

Quiz 11: Theories of Covalent Bonding

According to valence bond theory, the triple bond in ethyne (acetylene, C2H2) consists of

According to molecular orbital theory, what is the bond order in the O2+ ion?

Determine the shape (geometry) of PCl3 and then decide on the appropriate hybridization of phosphorus in this molecule. (Phosphorus is the central atom.)

Overlap of two sp2 hybrid orbitals produces a bond.

The angles between sp2 hybrid orbitals are 109.5°.

Which of the following statements relating to molecular orbital (MO) theory is incorrect?

The nitrosonium ion, NO+, forms a number of interesting complexes with nickel, cobalt, and iron. According to molecular orbital theory, which of the following statements about NO+ is correct?

Hybrid orbitals of the sp3d type occur in sets of four.