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

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

Question 1

Which statement best explains why water (H$$_2O) is $$considered a compound and not a mixture?

Accepted Answer

Water molecules have a fixed ratio of hydrogen to oxygen atoms.

Question 2

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

Accepted Answer

Ionic bonds involve the transfer of electrons between metals and nonmetals, while covalent bonds involve the sharing of electrons between two or more nonmetals.

Question 3

Which of the following elements is the most electronegative?

Accepted Answer

Fluorine

Question 4

Given the following electronegativity values: H = 2.1, Cl = 3.0, which type of bond is formed between hydrogen and chlorine?

Accepted Answer

Polar covalent bond

Question 5

Which of the following is the correct Lewis electron-dot symbol for oxygen?

Accepted Answer

O with six dots arranged around it, two on each of two sides and one on each of the other two sides

Question 6

Which compound is named correctly according to the rules for Type II ionic compounds?

Accepted Answer

FeCl$$_3 is $$named iron(III) chloride.

Question 7

What is the total number of valence electrons in the polyatomic ion NO$$_3^-$$?

Accepted Answer

$$5 + (3 	imes 6) + 1 = 24$$

Question 8

Which of the following statements about resonance structures is TRUE?

Accepted Answer

Resonance structures have the same skeletal formula but different electron arrangements.

Question 9

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

Accepted Answer

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

Question 10

Which molecule is an example of an exception to the octet rule due to an incomplete octet?

Accepted Answer

BF$$_3$$

Question 11

Which of the following best describes a coordinate covalent bond?

Accepted Answer

A covalent bond in which both electrons are donated by the same atom.

Question 12

Which of the following compounds contains a polyatomic ion?

Accepted Answer

Li$$_2Cr$_2O$_7$$

Question 13

What is the bond energy required to break all C-H bonds in one mole of methane (CH$$_4$$), given that the bond energy for a C-H bond is 414 kJ/mol?

Accepted Answer

$$4 	imes 414 = 1656 kJ/$$mol

Question 14

Which of the following is TRUE regarding the naming of molecular compounds?

Accepted Answer

Prefixes are used to indicate the number of atoms of each element.

Question 15

Which of the following best explains why ionic compounds have high melting points?

Accepted Answer

Strong electrostatic attractions between ions in the lattice require a large amount of energy to break.

Question 16

Which of the following is an example of a molecule with an expanded octet?

Accepted Answer

SF$$_6$$

Question 17

Which of the following is the correct order of steps for drawing a Lewis structure for a molecule?

Accepted Answer

Count valence electrons, connect atoms with single bonds, add lone pairs to exterior atoms, distribute remaining electrons to central atom, form multiple bonds if needed.

Question 18

Which of the following statements about formal charge is FALSE?

Accepted Answer

Formal charge should be placed on the least electronegative atom whenever possible.

Question 19

A molecule has three valid Lewis structures that differ only in the placement of electrons. What is the best description of the actual structure of the molecule?

Accepted Answer

A resonance hybrid that is intermediate between all resonance structures.

Question 20

Which of the following is a real-world example of a molecule that acts as a greenhouse gas due to its chemical bonding?

Accepted Answer

CO$$_2$$

Chapter 4: Chemical Bonding – General Chemistry Study Notes

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