Atomic Structure - AQA Revision Notes

Lecture by Chris Harris from AllergyTutors.com

Introduction

• Video covers AQA Atomic Structure.
• Powerpoints available for purchase.
• Tailored to the AQA specification.

The Atom

• Components:
  • Protons (positive charge)
  • Neutrons (neutral charge)
  • Electrons (negative charge)
• Relative Masses:
  • Proton: 1
  • Neutron: 1
  • Electron: 1/2000
• Element Representation:
  • Mass number (protons + neutrons) and Atomic number (protons).
  • Atoms are neutral (equal protons and electrons).

Ions and Isotopes

• Ions:
  • Different number of electrons and protons.
  • Examples:
    • Negative ion (O²⁻), gains electrons.
    • Positive ion (Na⁺), loses electrons.
• Isotopes:
  • Same number of protons, different number of neutrons (e.g., Carbon-12, Carbon-13, Carbon-14).

Historical Models of the Atom

• John Dalton (1803): Atoms are solid spheres.
• J.J. Thomson (1904): Plum pudding model, discovered electrons.
• Ernest Rutherford (1911): Discovered nucleus using the gold foil experiment; nucleus is small and dense.
• Niels Bohr (1913): Electrons in fixed shells; absorbed/emitted radiation corresponds to electron movement between shells.

Time-of-Flight Mass Spectrometer

• Stages:
  1. Vaporization: Turn sample into gas.
  2. Ionization: Electrospray technique; high voltage causes electron loss.
  3. Acceleration: Charged plates accelerate ions.
  4. Ion Drift: Ions travel at constant speed.
  5. Detection: Lighter ions detected first.
• Definitions:
  • Relative Atomic Mass, Relative Molecular Mass, and Relative Isotopic Mass.

Mass Spectra

• Axes:
  • Mass-to-charge ratio (m/z) and Abundance.
• Analysis:
  • Used to find isotopic composition.
  • Calculate relative atomic mass using isotopic abundance and m/z ratios.

Electron Configuration

• Subshells: S, P, D, F.
  • S: 1 orbital, holds 2 electrons.
  • P: 3 orbitals, holds 6 electrons.
  • D: 5 orbitals, holds 10 electrons.
  • F: 7 orbitals, holds 14 electrons.
• Notation: Example - 1s², 2s², 2p⁶.
• Filling Order: Lowest energy first, fill singly before pairing.
• Ions: Remove from highest energy level.
• Transition Metals: Unique electron configurations.

Ionisation Energies

• Definition: Energy required to remove an electron.
• Factors:
  • Shielding: More layers, less attraction.
  • Atomic Size: Larger atoms, weaker attraction.
  • Nuclear Charge: More protons, stronger attraction.
• Trends:
  • Down a group: Decreases (more shielding, larger atomic size).
  • Across a period: Increases (more protons).
• Exceptions:
  • Subshell energies (e.g., Aluminium, Sulfur).

Conclusion

• Powerpoints available for purchase from AllergyTutors.com.
• Covers key points for AQA Atomic Structure specification.