Question 1

Which of the following statements best describes the main limitation of Lewis structures in predicting molecular geometry?

Accepted Answer

Lewis structures cannot predict the three-dimensional shape of molecules and do not account for the role of orbitals.

Question 2

According to the VSEPR model, what is the primary factor that determines the structure around a given atom in a molecule?

Accepted Answer

Minimizing electron pair repulsions.

Question 3

A molecule with a steric number of 4 and no lone pairs on the central atom will have which electron-pair arrangement and bond angle?

Accepted Answer

Tetrahedral, $$109.5^{\circ}$$

Question 4

Which molecule below is expected to have a bent molecular structure due to the presence of lone pairs, given a steric number of 3?

Accepted Answer

Cl$$_2C ($$dichlorocarbene)

Question 5

Why do lone pairs compress the angles between bonding pairs in a molecule?

Accepted Answer

Lone pairs are closer to the nucleus and require more space than bonding pairs.

Question 6

Which of the following molecules would you expect to have a trigonal bipyramidal electron-pair arrangement?

Accepted Answer

SF$$_4$$

Question 7

What is the hybridization of the central atom in CO$$_2$$?

Accepted Answer

sp

Question 8

A double bond in a molecule consists of which combination of bonds?

Accepted Answer

One sigma ($$\sigma) $$bond and one pi ($$\pi) $$bond

Question 9

Which hybridization is required for an atom surrounded by three effective pairs?

Accepted Answer

sp$$^2$$

Question 10

In molecular orbital (MO) theory, what is the relationship between the number of atomic orbitals and the number of molecular orbitals formed?

Accepted Answer

The number of molecular orbitals is equal to the number of atomic orbitals used to construct them.

Question 11

Calculate the bond order for the H$$_2^+$$ ion using the formula $$	ext{Bond Order} = \frac{	ext{number of bonding electrons} - 	ext{number of antibonding electrons}}{2}. Is H$_2^+$$ expected to be stable?

Accepted Answer

Bond order = 0.5; H$$_2^+ is $$expected to be stable.

Question 12

Which of the following molecules is paramagnetic according to molecular orbital theory?

Accepted Answer

O$$_2$$

Question 13

In the MO diagram for O$$_2$$, what is the bond order and what does this imply about the strength of the O=O bond?

Accepted Answer

Bond order = 2; strong bond

Question 14

Which statement best explains why HF has a polar bond according to MO theory?

Accepted Answer

The bonding molecular orbital has higher electron probability closer to fluorine due to its lower energy 2p orbital.

Question 15

Which hybridization is associated with an octahedral arrangement of electron pairs?

Accepted Answer

d$$^2sp$^3$$

Question 16

A molecule has a center of positive charge and a center of negative charge. What property does this molecule possess?

Accepted Answer

It possesses a dipole moment.

Question 17

Which of the following best describes the difference between bonding and antibonding molecular orbitals?

Accepted Answer

Bonding MOs are lower in energy and have higher electron probability between nuclei, while antibonding MOs are higher in energy and have electron probability outside the space between nuclei.

Question 18

Which of the following molecules will have a net dipole moment?

Accepted Answer

PF$$_3$$

Question 19

Which of the following is true about paramagnetism?

Accepted Answer

Paramagnetism is associated with unpaired electrons and causes attraction to a magnetic field.

Question 20

Which step is NOT part of the VSEPR problem-solving strategy for determining molecular structure?

Accepted Answer

Maximize the number of lone pairs on the central atom.

Molecular Structure and Orbitals: VSEPR Theory and Electron Pair Geometry

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