AQA A-Level Chemistry Overview Lecture Notes

Introduction

• Welcome to the AQA Chemistry overview.
• Video timestamps in the description help navigate between topics.
• Useful for topic tests, paper revisions, and exams.
• Free revision guide on the website for detailed explanations. Links available below the video.
• Guides include predictive papers and thousands of multiple-choice questions.
• Live workshops and reviews are also mentioned.

Atomic Structure

Subatomic Particles

• Protons: In the nucleus, mass = 1, charge = +1.
• Neutrons: In the nucleus, mass = 1, charge = 0.
• Electrons: In shells, very small mass (1/1836 of a proton), charge = -1.

Important Concepts

• Relative charges are used as actual charges in Coulombs are very small.
• Atoms mostly empty space; nucleus diameter ≈ 10^-15 meters, total atom diameter ≈ 10^-10 meters.
• Structure evolved from 'blob' to current quantum model.

Isotopes & Mass Spectrometry

• Isotopes have the same number of protons, different neutrons (e.g., Carbon-12 and Carbon-14).
• Isotopes have the same electronic structure = same chemical properties.
• Mass Spectrometer: Time-of-Flight (TOF):
  • Steps: Ionization, Acceleration, Deflection, Detection to determine relative masses of isotopes.
• Mass number in periodic table = average of naturally occurring isotopes.

Electronic Structure

Quantum Models

• Periodic table divided into S, P, D, F blocks based on electron configurations.
• Orbital Diagrams: Electrons fill from lowest to highest energy levels with opposite spins.
• Simplified Example: Calcium – 1s² 2s² 2p⁶ 3s² 3p⁶ 4s².

Ionization Energy

• First Ionization Energy: Energy required to remove 1 electron from 1 mole of gaseous atoms.
• Second Ionization Energy: Energy required to remove an electron from 1 mole of gaseous +1 ions.
• Factors affecting ionization energy: Atomic radius, electron shielding, nuclear charge.
• Trends: Greater across periods, sharp drops at the start of each new period.

Chemical Calculations

Moles and Concentrations

• Moles = Mass / Molar Mass (n = m/Mr).
• Avogadro’s Number = 6.02 x 10²³ particles/mole.
• Conversions:
  • Celsius to Kelvin: +273.
  • cm³ to m³: ÷1,000,000.
  • dm³ to m³: ÷1,000.

Balancing Equations

• Essential for calculations and reactions.
• Must consider state symbols (s, l, g, aq).

Gas Laws

• Ideal Gas Law: PV = nRT.
• Important for calculating volumes and pressures of gases in reactions.

Practical Chemistry

Titration & Standard Solution Preparation

• Importance of accuracy (weighing, washing, mixing, and inverting solutions).
• Concordant results in titrations mean within 0.1 cm³.
• Rough titers help in knowing the rough number expected.

Energy Changes and Hess’s Law

• Enthalpy changes under standard conditions (298K, 1 atm, 1M solutions).
• Types of Enthalpy Changes: Formation, Combustion, Neutralization, Reaction.
• Calorimetry: Energy change calculation.

Organic Chemistry

Naming and Drawing Structures

• IUPAC rules: Longest chain, side chains, functional groups, and numbering.
• Functional groups change suffix: ‘-ane’, ‘-ene’, ‘-ol’, ‘-one’, etc.
• Use skeletal formulas for simplicity.

Reactions & Mechanisms

• Free Radical Substitution: Steps - Initiation, Propagation, Termination.
• Nucleophilic Substitution: Primary, Secondary, Tertiary alkane reactions with nucleophiles.
• Elimination Reactions: Creation of alkenes using bases.

Stereochemistry

• Structural Isomers: Chain, Position, Functional Group Isomers.
• Geometric (cis/trans) and Optical Isomerism.
• E/Z Naming: Based on atomic numbers of substituents.

Synthesis and Analytical Techniques

• Mass Spectrometry: Molecular ion peak and fragmentation.
• Infrared Spectroscopy: Characteristic absorption of bonds (data sheet provided in exams).

Periodicity and Reactivity Trends

Period 3 Reactions

• Reactions with water, oxygen, and acids/bases.
• Oxide formations: Trends across period 3.

Group 2 Metals: Alkaline Earth Metals

• Trends: Reactivity, ionization energy, reactions with water and acids.
• Uses for compounds like Mg(OH)₂ in medicine and CaO in flue gas desulfurization.

Halogens: Group 7 or 17

• Trends: Electronegativity, boiling/melting points, displacement reactions.
• Tests for halides and their practical applications.

Transition Metals and Complex Ions

Properties and Complex Formation

• Variable oxidation states, colorful compounds, and catalytic properties due to incomplete d sub-shell.
• Coordination Number: Number of ligands attached to the metal ion.
• Common Ligands: H₂O, NH₃, Cl⁻, etc.
• Ligand Substitution: Complex ion transitions, colors change based on ligand replacement.

Catalysts

• Examples: Fe in the Haber process, V₂O₅ in the Contact process.
• Examples of Catalyzed Reactions:
  • Manganese in Mn(II) and iodine-thiosulfate reactions (self-indicating titrations).
• Poisoning of Catalysts: Real-world impact and industrial considerations.

Amines and Protein Chemistry

Structure and Reactions

• Naming Amines: Primary, Secondary, Tertiary structures.
• Preparation Methods: From halogenoalkanes, nitriles, and reduction of nitro compounds.
• Reactivity: Acting as bases and nucleophiles.

Polymers and Biochemistry

• Condensation Polymers: Polyesters, Polyamides (e.g., Nylon, Kevlar).
• Biodegradability: Comparisons with addition polymers.
• Amino Acids & Proteins: Structure, zwitterions, levels of protein structure (primary, secondary, tertiary, quaternary).

Analytical Techniques

Chromatography

• Thin Layer Chromatography (TLC): Stationary phase, mobile phase, and calculating Rf values.
• Column & Gas Chromatography: Uses and separation techniques based on retention times.

Spectroscopy

• Proton NMR: Chemical shifts, integration, splitting patterns.
• Carbon NMR: Number and types of carbon environments.
• Utility in Identifying Compounds: Examples of peaks, splitting patterns, and environment details.

Conclusion

• Comprehensive review covering theoretical concepts, practical skills, and analytical techniques.
• Importance of clear understanding for exams and practical applications.
• Encouragement to utilize additional resources and practice for mastery.