Deck 4: Diatomic Molecules

Question 1

How do the bond enthalpies and bond lengths for the homonuclear diatomics, H₂, Li₂, Na₂ and K₂ change as the group is descended?

A) Bond lengths increase and bond enthalpies increase.
B) Bond lengths increase and bond enthalpies decrease.
C) Bond lengths decrease and bond enthalpies increase.
D) Bond lengths decrease and bond enthalpies decrease.

Answer 1

B

Question 2

For a homonuclear diatomic, the bond length is _____the distance of the atomic radius.

Answer 2

Twice

Question 3

In the figure below, the shape of the curve is dictated by which of the following factors? Please select all that apply.

A) At long distances there is no interaction between the atoms as the orbitals are not able to overlap.
B) At very short distances the atoms repel strongly as the positive nuclei come into close contact.
C) The equilibrium between repulsive and attractive forces generates the bond length between the atoms.
D) As the atoms become close enough together the orbitals overlap and the atoms are drawn together as bonding occurs.

Answer 3

A, B, C, D

Question 4

The Lewis model can be used to explain the differences in bond strength of F₂, O₂ and N₂.

Question 5

According to Lewis theory, a nitrogen atom in N₂ must share _ electrons to form a stable configuration.

Question 6

The dot and cross diagram for ammonia (NH₃) predicts that the shape at nitrogen is linear.

Question 7

The bonding of which of the following molecules can be explained by the Lewis model? Please select all that apply.

A) F₂
B) NO
C) PF₅
D) HF

Question 8

____________ species contain unpaired electrons and are affected by an external magnetic field.

Question 9

The electronegativity of an s or p block species is a constant irrespective of its oxidation state.

Question 10

Interhalogen compounds of the form XF exist where X is Cl, Br and I. The contribution from X⁺ F^- resonance form is more important than the contribution from the X^- F⁺ resonance form.

Question 11

Valence bond theory can be used to explain the trigonal planar structure of BF₃.

Question 12

It is possible for an electron in a molecular orbital to be found outside of the boundary created by the combined atomic orbitals.

Question 13

A σ (sigma) orbital has __________ symmetry about the internuclear axis.

Question 14

Match the bond order of the dihydrogen species with the appropriate species.
-H₂

A) 1
B) 0.5
C) 0

Question 15

Match the bond order of the dihydrogen species with the appropriate species.
-H₂^-

A) 1
B) 0.5
C) 0

Question 16

Match the bond order of the dihydrogen species with the appropriate species.
-H₂^2-

A) 1
B) 0.5
C) 0

Question 17

Taking z as the internuclear axis, how would the orbital formed from the bonding combination of two d_z² orbitals be labelled?

A) σ_u
B) σ_g
C) π_g
D) π_u

Question 18

The magnetic properties of O₂ are very important as they are used to monitor the presence of oxygen in places where oxygen levels are essential. Which of the follow models suggests that dioxygen should be paramagnetic? Please select all that apply.

A) The Lewis model
B) Valence bond theory
C) Molecular orbital theory
D) All of the above

Question 19

Draw the molecular orbital diagram of OF⁺ to determine the bond order. OF⁺ can exist.

Question 20

MgB₂ is a superconducting compound consisting of Mg²⁺ cations and B₂^2- anions. The diboride anion in this compound is diamagnetic.

Question 21

Which of the following statements are true in relation to homonuclear diatomics? Please select all that apply.

A) Any combination of two atomic orbitals can form a bonding and an antibonding molecular orbital combination.
B) For B₂, C₂ and N₂, the σ bonding combination of the p orbitals are lower in energy than the $\pi$ bonding combination.
C) For O₂, the energy level order depends on independent overlap of the s orbitals and p orbitals.
D) For B₂, C₂ and N₂, the energy level order is affected by the mixing of s and p orbitals.

Question 22

The same general principles apply to constructing molecular orbital diagrams for heteronuclear diatomics as for homonuclear diatomics?

Question 23

Which of the following statements relating to the molecular orbital energy level diagram of LiH are true? Please select all that apply.

A) Two atomic orbitals, one from each atom, create two molecular orbitals on the LiH molecule.
B) The antibonding combination is labelled 2σ_u.
C) The 1s orbital of Li and the 1s orbital of H are used to form the molecular orbitals.
D) The out-of-phase combination has a larger contribution from the Li atomic orbital.

Question 24

The wavefunction expression for the antibonding molecular orbital (1σ) in LiH is $\Psi$ _{out of phase} = N[ $\phi$ _H(1s) - $\lambda$$\phi$ _Li(2s)] where λ < 1.

Question 25

In HF, the single bond formed between H and F by the overlap of the 1s on hydrogen with the ___ on F.

Question 26

The orbital containing electrons and of the highest energy is known as the _____

Question 27

Which of the following statements relating to the diagram of CO are true? Please select all that apply.

A) Adding electrons to form an anion will lower the bond order.
B) CO is paramagnetic.
C) Adding electrons to form an anion will increase the bond order.
D) CO is diamagnetic.