Question 1

Which of the following best describes the difference between an ionic bond and a covalent bond according to the Lewis model?

Accepted Answer

An ionic bond involves the transfer of electrons from a nonmetal to a metal, while a covalent bond involves the sharing of electrons between nonmetals.

Question 2

How many valence electrons are present in a phosphorus atom, and how is this represented in its Lewis structure?

Accepted Answer

Phosphorus has 5 valence electrons, represented by five dots around the symbol P.

Question 3

Which of the following molecules is an example of a molecule with a double bond, and why does it form a double bond?

Accepted Answer

Oxygen (O2); it forms a double bond because each oxygen atom needs to share two pairs of electrons to achieve an octet.

Question 4

Which of the following best explains why water (H2O) is a polar molecule?

Accepted Answer

Water has polar bonds and a bent molecular geometry, so the dipole moments do not cancel.

Question 5

Which of the following is the correct Lewis structure for carbon dioxide (CO2)?

Accepted Answer

$$\mathrm{O} = \mathrm{C} = \mathrm{O}$$

Question 6

A molecule of ammonia (NH3) has which of the following molecular geometries, and what is the approximate bond angle?

Accepted Answer

Trigonal pyramidal, 107°

Question 7

Which of the following statements about resonance structures is correct?

Accepted Answer

Resonance structures are equivalent Lewis structures for the same molecule, and the true structure is an average of them.

Question 8

Which of the following best describes the effect of electronegativity difference ($$\Delta EN) on $$bond type?

Accepted Answer

A $$\Delta EN$$ greater than 2.0 results in an ionic bond.

Question 9

Which of the following is an exception to the octet rule?

Accepted Answer

Boron trifluoride (BF3)

Question 10

A molecule has three electron groups around the central atom and no lone pairs. What is its electron geometry and bond angle?

Accepted Answer

Trigonal planar, 120°

Question 11

Which of the following best explains why oil and water do not mix?

Accepted Answer

Oil molecules are nonpolar and water molecules are polar, so water molecules attract each other and exclude oil.

Question 12

Which of the following is the correct sequence of steps for drawing a Lewis structure for a covalent compound?

Accepted Answer

Write the skeletal structure, calculate total valence electrons, distribute electrons to give octets, form double/triple bonds if needed.

Question 13

Which of the following molecules is nonpolar, despite having polar bonds?

Accepted Answer

Carbon dioxide ($$\mathrm{CO}_2)$$

Question 14

Which of the following best describes the role of molecular shape in the effectiveness of artificial sweeteners?

Accepted Answer

Artificial sweeteners are effective because their molecular shape allows them to fit into taste receptor sites, triggering a sweet response.

Question 15

Which of the following statements about free radicals is correct?

Accepted Answer

Free radicals are molecules with an odd number of valence electrons and are highly reactive.

Question 16

Which of the following best describes the geometry and bond angles of methane ($$\mathrm{CH}_4$$)?

Accepted Answer

Tetrahedral geometry with bond angles of $$109.5^{\circ}$$

Question 17

Which of the following is true about the polarity of a molecule with four identical polar bonds arranged tetrahedrally?

Accepted Answer

The molecule is nonpolar because the bond dipoles cancel.

Question 18

Which of the following best explains why soap is effective at removing grease from hands?

Accepted Answer

Soap molecules have a polar head that interacts with water and a nonpolar tail that interacts with grease, allowing water and grease to mix.

Chemical Bonding: Lewis Structures, Molecular Geometry, and Polarity

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