Q: Which of the following is the correct formula for calculating the formal charge on an atom in a Lewis structure?

$$\text{Formal charge} = \text{valence electrons} - \frac{1}{2}(\text{bonding electrons}) - \text{nonbonding electrons}$$

Question 1

Which of the following statements best explains why sodium chloride ($$\mathrm{NaCl}) $$has a high melting point?

Accepted Answer

Because $$\mathrm{NaCl} is $$composed of ions held together by strong electrostatic attractions in a crystalline lattice.

Question 2

Which of the following elements is most likely to form compounds that violate the octet rule by having more than eight valence electrons?

Accepted Answer

Phosphorus ($$\mathrm{P})$$

Question 3

Which of the following best describes a polar covalent bond?

Accepted Answer

A bond in which electrons are shared unequally, resulting in partial charges on the atoms.

Question 4

Which of the following molecules is expected to have a linear molecular geometry according to the VSEPR model?

Accepted Answer

$$\mathrm{CO_2$}$$

Question 5

What is the formal charge on the central atom in the Lewis structure of $$\mathrm{NO_3$^-} ($$nitrate ion)?

Accepted Answer

0

Question 6

Which of the following best explains why the bond angle in $$\mathrm{H_2O} is $$less than $$109.5^\circ$$?

Accepted Answer

Because lone pairs on oxygen repel bonding pairs more strongly, compressing the bond angle.

Question 7

Which of the following is the correct order of increasing bond polarity for the following bonds: $$\mathrm{C-H}$$, $$\mathrm{N-H}$$, $$\mathrm{O-H}$$?

Accepted Answer

$$\mathrm{C-H} \u003c \mathrm{N-H} \u003c \mathrm{O-H}$$

Question 8

Which of the following molecules contains a central atom with sp$$^2$$ hybridization?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 9

A molecule has four electron domains (two bonding pairs and two lone pairs) around its central atom. What is its molecular geometry?

Accepted Answer

Bent

Question 10

Which of the following best describes a sigma ($$\sigma) $$bond?

Accepted Answer

A bond formed by the head-to-head overlap of orbitals, with electron density along the internuclear axis.

Question 11

Which of the following is a correct statement about the formation of ionic bonds?

Accepted Answer

Ionic bonds form when a metal atom transfers electrons to a nonmetal atom, resulting in oppositely charged ions.

Question 12

Which of the following molecules or ions is an example of an expanded octet?

Accepted Answer

$$\mathrm{PF_5$}$$

Question 13

Which of the following best explains why $$\mathrm{$$BeCl_2$$}$$ forms linear molecules?

Accepted Answer

Because beryllium uses sp hybrid orbitals, resulting in two electron domains arranged linearly.

Question 14

Which of the following is the correct formula for calculating the formal charge on an atom in a Lewis structure?

Accepted Answer

$$	ext{Formal charge} = 	ext{valence electrons} - \frac{1}{2}(	ext{bonding electrons}) - 	ext{nonbonding electrons}$$

Question 15

Which of the following statements about resonance structures is correct?

Accepted Answer

Resonance structures are different possible arrangements of electrons in a molecule, with the same arrangement of atoms.

Question 16

Which of the following molecules has a dipole moment?

Accepted Answer

$$\mathrm{H_2O}$$

Question 17

A molecule has five electron domains: three bonding pairs and two lone pairs. What is its molecular geometry?

Accepted Answer

T-shaped

Question 18

Which of the following best describes the difference between sigma ($$\sigma) $$and pi ($$\pi) $$bonds?

Accepted Answer

$$\sigma$$ bonds result from head-to-head overlap, while $$\pi$$ bonds result from side-to-side overlap of p orbitals.

Question 19

Which of the following is a property of most covalent compounds?

Accepted Answer

They have low melting points and are often found as gases or liquids at room temperature.

Question 20

Which of the following best explains why $$\mathrm{O_3$} ($$ozone) has two identical $$\mathrm{O-O}$$ bond lengths, even though its Lewis structure suggests otherwise?

Accepted Answer

Because ozone has resonance structures, resulting in bond lengths that are an average of single and double bonds.

Basic Concepts of Chemical Bonding: Ionic and Covalent Bonds

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