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

$\text{Formal charge} = \text{number of valence electrons} - (\text{number of non-bonding electrons} + \frac{1}{2} \times \text{number of bonding electrons})$

Question 1

Which of the following statements best describes valence electrons?

Accepted Answer

Valence electrons are the electrons in the highest principal quantum number and any in partially filled d and f orbitals.

Question 2

Which of the following compounds would you expect to have the highest lattice energy based on the data provided?

Accepted Answer

MgO

Question 3

According to Coulomb's Law, which change will increase the attractive force between two ions in an ionic compound?

Accepted Answer

Decreasing the distance $d$ between the ions

Question 4

Which of the following molecules is an exception to the octet rule because it has less than an octet of electrons?

Accepted Answer

BF$_3$

Question 5

What is the formal charge on the central nitrogen atom in the nitrate ion ($NO_3^-$) if the Lewis structure has one double bond and two single bonds to oxygen?

Accepted Answer

$0$

Question 6

Which of the following best explains why HF has a much higher dipole moment than HI?

Accepted Answer

The electronegativity difference between H and F is much greater than between H and I.

Question 7

Which step in drawing a Lewis structure involves assigning formal charges to atoms?

Accepted Answer

Step 5: Try multiple bonds if there are not enough electrons on the central atom to form an octet, using formal charge assignment.

Question 8

Which of the following bonds is most likely to be considered non-polar covalent?

Accepted Answer

HI

Question 9

Given the following bond enthalpies: $D(H-H) = 436$ kJ/mol, $D(Cl-Cl) = 243$ kJ/mol, $D(H-Cl) = 431$ kJ/mol, calculate the enthalpy change for the reaction $H_2 + Cl_2 \rightarrow 2HCl$.

Accepted Answer

$-184$ kJ

Question 10

Which molecule below is a good example of resonance, where all bonds are of equal length?

Accepted Answer

O$_3$

Question 11

Which of the following statements about electronegativity is correct?

Accepted Answer

Electronegativity is the ability of an atom in a molecule to attract electrons to itself.

Question 12

Which of the following ions would you expect to have the largest lattice energy when paired with F$^-$?

Accepted Answer

Li$^+$

Question 13

Which of the following molecules is an exception to the octet rule because it has more than an octet of electrons?

Accepted Answer

PF$_5$

Question 14

What is the main reason for the stability of resonance structures in molecules like ozone ($O_3$)?

Accepted Answer

Resonance structures distribute electron density symmetrically, lowering the overall energy.

Question 15

Which of the following best describes the difference between ionic and covalent bonds?

Accepted Answer

Ionic bonds involve the transfer of electrons, while covalent bonds involve the sharing of electrons.

Question 16

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{number of valence electrons} - (	ext{number of non-bonding electrons} + \frac{1}{2} 	imes 	ext{number of bonding electrons})$

Question 17

Which of the following molecules contains an atom with an odd number of electrons, making it an exception to the octet rule?

Accepted Answer

NO

Question 18

If the electronegativity difference $\Delta x$ between two atoms is 2.5, what type of bond is most likely formed?

Accepted Answer

Ionic

Question 19

Which of the following best describes the relationship between bond length and bond order in covalent bonds?

Accepted Answer

Bond length decreases as bond order increases.

Question 20

Which of the following is true about the Born-Haber cycle for the formation of NaCl?

Accepted Answer

It includes steps such as ionization energy, electron affinity, and lattice energy.

Chapter 10: Basic Concepts of Chemical Bonding – Study Notes

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