Question 1

According to valence bond theory, which condition is necessary for a covalent bond to form between two atoms?

Accepted Answer

An orbital on one atom must occupy a portion of the same region of space as an orbital on the other atom, and the total number of electrons in both orbitals must not exceed two.

Question 2

Which statement best explains why the H–H bond in $$\mathrm{H}_2 is $$stronger than the H–Cl bond in HCl?

Accepted Answer

The H–H bond involves the overlap of two 1s orbitals, which have greater overlap than the 1s and 3p orbitals in HCl.

Question 3

How many sp$$^2$$ hybrid orbitals are formed when one s orbital and two p orbitals combine?

Accepted Answer

Three

Question 4

Which geometric arrangement corresponds to sp$$^3d $$hybridization?

Accepted Answer

Trigonal bipyramidal

Question 5

In methane ($$\mathrm{CH}_4$$), what is the hybridization of the central carbon atom and how many identical bonds does it form?

Accepted Answer

sp$$^3$$ hybridization; four identical bonds

Question 6

Which step is NOT part of the procedure for describing bonding about any atom in a molecule using valence bond theory?

Accepted Answer

Calculating the formal charge of each atom

Question 7

In boron trifluoride ($$\mathrm{BF}_3$$), what is the hybridization of the boron atom and what is the molecular geometry?

Accepted Answer

sp$$^2$$; trigonal planar

Question 8

Which hybrid orbitals are present in the nitrogen atom of $$\mathrm{N}_2\mathrm{F}_4$$ and how do they participate in bonding?

Accepted Answer

sp$$^3$$ hybrid orbitals; form three bonds and one lone pair

Question 9

In the $$\mathrm{ClF}_2^-$$ ion, which hybridization is used by the central chlorine atom and how many lone pairs occupy the equatorial positions?

Accepted Answer

sp$$^3d$$; three lone pairs

Question 10

Which statement correctly describes the difference between a sigma ($$\sigma) $$bond and a pi ($$\pi) $$bond?

Accepted Answer

A $$\sigma$$ bond is formed by overlap along the bond axis, while a $$\pi$$ bond is formed by sideways overlap of parallel p orbitals.

Question 11

Why does the overlap of parallel p orbitals in a $$\pi$$ bond restrict rotation around a double bond, as seen in cis-trans isomerism?

Accepted Answer

Because the sideways overlap of p orbitals fixes the geometric positions of substituents

Question 12

In formaldehyde ($$\mathrm{CH}_2\mathrm{O}$$), what is the hybridization of the carbon atom and how are the C–O bonds formed?

Accepted Answer

sp$$^2$$; one C–O $$\sigma$$ bond from sp$$^2$$ and one C–O $$\pi$$ bond from 2p orbitals

Question 13

Which statement about molecular orbitals is correct?

Accepted Answer

Bonding molecular orbitals are obtained by adding atomic orbitals and are concentrated between nuclei.

Question 14

What is the bond order of the $$\mathrm{H}_2^+$$ ion, and what does this imply about its stability?

Accepted Answer

Bond order = $$\frac{1}{2}$$; the ion has a weak but existent bond

Question 15

Given the molecular electron configuration of $$\mathrm{F}_2 as$$ $$\mathrm{KK}(\sigma_{2s})^2$(\sigma_{2s}^*)^2$(\pi_{2p})^4$(\sigma_{2p})^2$(\pi_{2p}^*)^4$, what is the bond order and magnetic character of the molecule?

Accepted Answer

Bond order = 1; diamagnetic

Question 16

Which factor does NOT increase the strength of the interaction between two atomic orbitals to form molecular orbitals?

Accepted Answer

Large energy difference between the interacting orbitals

Question 17

What is the bond order of $$\mathrm{Be}_2$$ and what does this indicate about its stability?

Accepted Answer

Bond order = 0; the molecule is not stable

Question 18

Which of the following molecules is predicted to be paramagnetic based on its molecular orbital configuration?

Accepted Answer

$$\mathrm{O}_2$$

Valence Bond Theory and Molecular Orbital Theory: Structured Study Notes - Chapter 11 - Part 2

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