Question 1

According to valence bond theory, what is required for a covalent bond to form between two hydrogen atoms?

Accepted Answer

The overlap of two half-filled 1s orbitals, each containing one unpaired electron.

Question 2

The energy diagram for the interaction of two hydrogen atoms shows a minimum at a certain H–H distance. What does this minimum represent?

Accepted Answer

The bond length and bond energy of the H$$_2$$ molecule.

Question 3

In the molecule H$$_2S$$, which orbitals on sulfur overlap with the hydrogen 1s orbitals to form bonds?

Accepted Answer

The two half-filled 3p orbitals on sulfur.

Question 4

Why does carbon in methane (CH$$_4) $$form four equivalent bonds with bond angles of 109.5$$^	ext{o}$$ instead of two or three bonds at 90$$^	ext{o}$$ angles?

Accepted Answer

Carbon undergoes sp$$^3$$ hybridization, forming four equivalent hybrid orbitals.

Question 5

Which of the following best describes the hybridization of the central carbon atom in formaldehyde (CH$$_2O$$)?

Accepted Answer

sp$$^2$$ hybridization, with one unhybridized p orbital forming a π bond with oxygen.

Question 6

Which statement about σ (sigma) and π (pi) bonds is correct?

Accepted Answer

A σ bond results from end-to-end overlap of orbitals, while a π bond results from side-to-side overlap of parallel p orbitals.

Question 7

Why can't double bonds freely rotate, as shown in molecules like 1,2-dichloroethene?

Accepted Answer

The presence of a π bond restricts rotation because breaking the π bond requires significant energy.

Question 8

What is the hybridization of the central atom in SF$$_6 ($$sulfur hexafluoride)?

Accepted Answer

sp$$^3d$^2$$

Question 9

Which hybridization and geometry are expected for an atom with three electron groups around it?

Accepted Answer

sp$$^2$$ hybridization and trigonal planar geometry

Question 10

In acetylene (C$$_2H$_2$$), what is the hybridization of each carbon atom and how are the triple bonds formed?

Accepted Answer

Each carbon is sp hybridized; the triple bond consists of one σ bond and two π bonds.

Question 11

Which of the following molecules is predicted by molecular orbital theory to be paramagnetic?

Accepted Answer

O$$_2$$

Question 12

What is the bond order of the H$$_2$$ molecule according to molecular orbital theory?

Accepted Answer

$$\frac{2-0}{2} = 1$$

Question 13

Why does the He$$_2$$ molecule not exist according to molecular orbital theory?

Accepted Answer

The bond order is zero because the number of electrons in bonding and antibonding orbitals is equal.

Question 14

As bond order increases in a molecule, what happens to the bond length and bond energy?

Accepted Answer

Bond length decreases and bond energy increases.

Question 15

Which of the following best explains why O$$_2 is $$attracted to a magnet?

Accepted Answer

O$$_2$$ has unpaired electrons in its molecular orbitals, making it paramagnetic.

Question 16

A molecule has five electron groups around its central atom. What is the expected hybridization and geometry?

Accepted Answer

sp$$^3d $$hybridization and trigonal bipyramidal geometry

Question 17

Which of the following statements about hybridization is correct?

Accepted Answer

The number of hybrid orbitals formed equals the number of atomic orbitals combined.

Question 18

In the context of real-world applications, why is the concept of hybridization important for understanding the structure of drugs like aspirin?

Accepted Answer

Hybridization explains the three-dimensional arrangement of atoms, which affects the drug's biological activity.

Question 19

Which of the following is a consequence of the presence of a π bond in a molecule?

Accepted Answer

Restricted rotation around the bond axis, leading to cis-trans isomerism.

Valence Bond Theory and Molecular Orbital Theory: Hybridization and Bonding in Molecules

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