3. Chemical Bonds Flashcards
State the octet rule.
The octet rule reasons that the closest noble gas configuration of most elements consists of eight valence electrons. The exception to this rule is hydrogen (H), whose closest noble gas is helium (He) and has only two valence electrons. Elements belonging to the second period of the periodic table best respond to this rule.
What are ionic compounds?
These are chemical compounds in which elements bond ionically. The compound is neutral overall but consists of positive and negative ions joined through electrostatic forces.
What is a Chemical Bond?
A force holding atoms or molecules together.
Determines a compound’s properties.
Can be predicted and verified experimentally.
What is the Lewis Dot Formula?
Represents valence electrons using dots around an element’s symbol.
Helps visualize, interpret, and predict bonding.
Electrons can be shared (covalent) or donated (ionic).
What is the Octet Rule?
Atoms aim to achieve 8 valence electrons for stability.
Achieved by sharing, donating, or stealing electrons.
Based on noble gas electron configurations.
What are Ionic Bonds?
Formed by electrostatic attraction between cations (+) and anions (-).
Example: NaCl (sodium chloride) → Na⁺ donates, Cl⁻ gains electron.
Creates crystalline structures with unique optical & physical properties.
Why do Ionic Bonds Form?
Depends on lattice energy, which measures ionic compound stability.
Lattice energy: Energy needed to separate ions in a solid.
Higher lattice energy = stronger bond, higher melting point.
What is Coulomb’s Law?
Describes electrostatic forces in an ionic bond.
Energy is proportional to the product of charges & inversely proportional to distance.
Explains why smaller, highly charged ions form stronger bonds.
What is the Born-Haber Cycle?
A method to calculate lattice energy using Hess’s Law.
Breaks ionic bond formation into 5 steps, including electron transfer & lattice formation.
Example: NaCl has a high lattice energy, leading to a melting point of 801°C.
What is Hess’s Law?
The total energy change in a reaction is independent of the path taken.
Used in the Born-Haber cycle to determine lattice energy.
Helps explain why ionic compounds are stable & have high melting points.
What is a Covalent Bond?
A bond where electrons are shared between atoms.
Occurs when electronegativity values are similar (unlike ionic bonds).
Represented by a single solid line (—) between elements.
What is a Pure Covalent Bond?
Electrons are shared equally between identical atoms.
Example: H₂ (hydrogen gas), F₂ (fluorine gas).
What is a Double Covalent Bond?
A bond where two pairs of electrons are shared.
Example: O₂ (oxygen gas), CO₂ (carbon dioxide).
Lone pairs = Valence electrons not involved in bonding.
What is a Polar Covalent Bond?
Electrons are shared unequally due to differences in electronegativity.
Example: H₂O (water), NH₃ (ammonia).
What Determines Electron Sharing?
Electronegativity: An atom’s ability to attract electrons.
Higher electronegativity = stronger pull on electrons.
Fluorine (F) has the highest electronegativity.
Trends in Electronegativity
Increases across a period (left → right).
Decreases down a group (top → bottom).
Large electronegativity difference → Ionic bond formation.
How to Classify Bonds?
Nonpolar Covalent: Electronegativity difference = 0 – 0.4.
Polar Covalent: Electronegativity difference = 0.5 – 1.7.
Ionic Bond: Electronegativity difference > 1.7.
What is Metallic Bonding?
A bond found in metallic solids.
Features positive atomic cores surrounded by a “sea” of delocalized electrons.
Why Are Metals Strong?
Cohesive forces from metallic bonding provide strength.
More valence electrons → Stronger bonds.
Why Are Metals Good Conductors?
Delocalized electrons move freely through the structure.
Higher electrical conductivity than most elements.
What is Ductility?
The ability to be stretched or deformed without breaking.
Caused by nondirectional metallic bonds.
Example: Jewelry, wires, and metal sheets.
Why Do Metals Shine?
Reflect visible light, giving them a metallic luster.
Optical properties arise from electron interactions.
Why Do Metals Corrode?
Mixed factors, but metallic bonding plays a key role.
Exposure to oxygen and moisture leads to oxidation (e.g., rusting in iron).
What Are Intermolecular Forces?
Forces that attract molecules to one another.
Weaker than intramolecular forces (bonds between atoms).
Important in liquids and solids.
