Question 1

According to the Valence Shell Electron Pair Repulsion (VSEPR) theory, what determines the shape of a molecule?

Accepted Answer

The arrangement of electron pairs (bonding and nonbonding) around the central atom

Question 2

In the VSEPR model, how are double and triple bonds treated when predicting molecular shapes?

Accepted Answer

Double and triple bonds are treated as a single group of electrons

Question 3

What is the electron geometry of water ($$\mathrm{H_2O}) $$according to VSEPR theory?

Accepted Answer

Tetrahedral

Question 4

Why does the molecular geometry of $$\mathrm{H_2O}$$ differ from its electron geometry?

Accepted Answer

Because there are lone pairs of electrons on the central atom

Question 5

For the molecule $$\mathrm{SO_3$^{2-}}$$, what is the electron geometry around the central sulfur atom?

Accepted Answer

Tetrahedral

Question 6

In a trigonal bipyramidal geometry, why are lone pairs always placed in the equatorial position?

Accepted Answer

Because lone pairs experience less repulsion in the equatorial position

Question 7

What is the molecular geometry of $$\mathrm{$$XeF_4$$}$$?

Accepted Answer

Square planar

Question 8

Which of the following molecules has more than one central atom, requiring separate VSEPR analysis for each?

Accepted Answer

Acetic acid ($$\mathrm{CH_3COOH})$$

Question 9

Which electron geometry is associated with four electron groups around a central atom?

Accepted Answer

Tetrahedral

Question 10

Why do molecules with the same electron geometry (e.g., $$\mathrm{CH_4$}$$, $$\mathrm{NH_3$}$$, $$\mathrm{H_2O}) $$have different bond angles?

Accepted Answer

Because lone pairs decrease the bond angle between bonding pairs

Question 11

Which of the following has the smallest bond angle: $$\mathrm{NH_3$} or$$ $$\mathrm{NO_3$^-}$$?

Accepted Answer

$$\mathrm{NH_3$}$$

Question 12

What is a dipole moment in a molecule?

Accepted Answer

A measure of the separation of charge in a molecule, with one end slightly positive and the other slightly negative

Question 13

Why can a molecule with polar bonds still be nonpolar overall?

Accepted Answer

Because the bond dipoles are vector quantities and can cancel each other out

Question 14

Which molecule has a net dipole moment: $$\mathrm{CO_2$} or$$ $$\mathrm{H_2O}$$?

Accepted Answer

$$\mathrm{H_2O}$$

Question 15

What is the electron geometry of the labeled oxygen in aspartic acid (see image)?

Accepted Answer

Tetrahedral

Question 16

According to valence bond theory, what is required for a covalent bond to form?

Accepted Answer

The orbitals on two atoms must overlap

Question 17

What is the shared region of space between overlapping orbitals called?

Accepted Answer

Atomic overlap

Question 18

In the case of $$\mathrm{H_2S}$$, what is the valence electron configuration of sulfur?

Accepted Answer

$$3p^4$$

Question 19

Why does valence bond theory sometimes fail to explain observed molecular geometries, such as the tetrahedral shape of methane ($$\mathrm{CH_4$}$$)?

Accepted Answer

Because it does not account for hybridization of atomic orbitals

Chapter 10: Chemical Bonding II – Molecular Shapes and Valence Bond Theory

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