Topic 4 Bonding And Lewis Structure

Question 1

What are the three main types of chemical bonds?

Answer 1

Ionic, covalent, and metallic

Question 2

What is the octet rule?

Answer 2

Atoms tend to gain, lose, or share electrons to achieve a full outer shell of 8 electrons, resembling the electron configuration of noble gases

Question 3

What is the main difference between ionic and covalent bonds?

Answer 3

Ionic bonds result from the transfer of electrons, while covalent bonds result from the sharing of electrons.

Question 4

Define electronegativity.

Answer 4

The ability of an atom to attract a shared pair of electrons in a covalent bond.

Question 5

What is a Lewis structure?

Answer 5

A representation of a molecule that shows all valence electrons, including bonding and non-bonding (lone) pairs.

Question 6

What kind of bond forms between two nonmetals?

Answer 6

Covalent bond.

Question 7

What kind of bond forms between a metal and a nonmetal?

Answer 7

Ionic bond.

Question 8

Why are metallic bonds conductive?

Answer 8

Because their delocalized electrons can move freely throughout the metallic lattice.

Question 9

Why do ionic compounds have high melting points?

Answer 9

Due to the strong electrostatic forces of attraction between oppositely charged ions.

Question 10

How many electrons are shared in a double covalent bond?

Answer 10

Four electrons.

Question 11

Draw the Lewis structure for water (H₂O).

Answer 11

Oxygen has 6 valence electrons, forms two single bonds with two hydrogen atoms, and has two lone pairs.

Question 12

Draw the Lewis structure for methane (CH₄).

Answer 12

Carbon forms four single bonds with four hydrogen atoms and has no lone pairs.

Question 13

What is the formula of the ionic compound formed between magnesium and oxygen?

Answer 13

MgO

Question 14

Predict the type of bonding in CO₂ and explain why.

Answer 14

Covalent bonding, because it is formed between two nonmetals (carbon and oxygen).

Question 15

Which has a smaller radius: Cl or Cl⁻? Why?

Answer 15

Cl⁻ is larger because it gains an electron, increasing electron-electron repulsion in the outer shell.

Question 16

How do you determine the central atom in a Lewis structure?

Answer 16

The central atom is usually the least electronegative element (except hydrogen).

Question 17

Why do lone pairs affect molecular geometry?

Answer 17

Lone pairs repel more strongly than bonding pairs, distorting bond angles.

Question 18

Describe the bonding in a diatomic nitrogen molecule (N₂).

Answer 18

N₂ has a triple bond, sharing six electrons between two nitrogen atoms to satisfy the octet rule.

Question 19

Which element is most likely to violate the octet rule, and why?

Answer 19

Phosphorus or sulfur, because they can expand their octet by using d-orbitals.

Question 20

Explain why ionic bonds are stronger than covalent bonds in some cases.

Answer 20

Ionic bonds involve the electrostatic attraction between ions, which is typically stronger than the overlap of electron orbitals in covalent bonds.

Question 21

Draw the Lewis structure for CO₂.

Answer 21

• Carbon is the central atom with 4 valence electrons.
• Each oxygen atom (6 valence electrons) forms a double bond with carbon to complete the octet for all three atoms.
• Structure: O = C = O

Question 22

What type of bond forms in AlCl₃? Explain your reasoning.

Answer 22

• AlCl₃ primarily exhibits covalent bonding because aluminum shares its three valence electrons with chlorine.
• However, due to the polar nature of Al-Cl bonds (difference in electronegativity), the bonding has partial ionic character.

Question 23

Draw the Lewis structure for ammonia (NH₃), and predict its molecular shape

Answer 23

Lewis structure:
Nitrogen (5 valence electrons) forms three single bonds with three hydrogen atoms. Nitrogen also has one lone pair.

Molecular Shape:
Trigonal pyramidal due to the lone pair causing a distortion.

Question 24

Why does NaCl dissolve in water? Explain using bonding principles

Answer 24

• NaCl dissolves because water is polar. The partially negative oxygen in water attracts the Na⁺ ions, and the partially positive hydrogens attract the Cl⁻ ions. This breaks the ionic bonds in NaCl and forms ion-dipole interactions.

Question 25

Compare the bonding in graphite and diamond.

Answer 25

Graphite:

Each carbon atom forms three covalent bonds, creating layers of hexagonal structures. The fourth electron is delocalized, allowing electrical conductivity
Diamond:

Each carbon atom forms four covalent bonds in a tetrahedral structure, resulting in a very hard material with no free electrons (non-conductive).

Question 26

What does the term “oxidation” mean in redox chemistry?

Answer 26

Oxidation refers to the ‘loss of electrons’ or an increase in oxidation number.

Question 27

What does the term “reduction” mean in redox chemistry?

Answer 27

Reduction refers to the ‘gain of electrons’ or a decrease in oxidation number.