AQA Chemistry A-level: Atomic Structure Overview

Plum Pudding Model

Early atomic model with positive sphere and negative charges.

Electron Shell Model

Atoms have a dense nucleus with orbiting electrons.

Rutherford Scattering Experiment

1911 experiment confirming the atomic nucleus existence.

Nucleus

Central part of an atom containing protons and neutrons.

Proton

Positively charged particle in the atomic nucleus.

Neutron

Neutral particle in the atomic nucleus.

Electron

Negatively charged particle orbiting the nucleus.

Relative Charge

Charge comparison of particles: +1, 0, -1.

Relative Mass

Mass comparison: proton/neutron = 1, electron = 1/1840.

Maximum Electrons per Shell

Calculated using formula 2n², where n is shell number.

Mass Number (A)

Sum of protons and neutrons in an atom.

Atomic Number (Z)

Number of protons in an atom.

Relative Atomic Mass (Ar)

Mean mass of an atom relative to carbon-12.

Isotopes

Atoms with same protons, different neutrons and mass.

Ions

Charged particles formed by electron loss or gain.

Mass Spectrometry

Technique to identify isotopes and relative atomic mass.

Time of Flight (TOF)

Mass spectrometry measuring ion travel time to detector.

Ionisation

Process of creating charged ions from neutral atoms.

Acceleration

Positively charged ions are accelerated towards detection.

Ion Drift

Ions follow curved paths due to magnetic fields.

Detection

Current produced when ions hit detection plate.

Analysis

Current values used to produce isotope abundance spectra.

Mass to Charge Ratio (m/z)

Ratio affecting ion path curvature in mass spectrometry.

Electron Configuration

Arrangement of electrons in atomic orbitals.

Electron Orbitals

Regions where electrons are likely to be found.

Orbital Types

s, p, d, and f orbitals with distinct shapes.

Spin

Electrons in orbitals must have opposite spins.

Ionisation Energy

Energy needed to remove one mole of electrons.

Trends in Ionisation Energy

Varies across periods and groups in the periodic table.

Exceptions to Electron Configuration Rules

Unpaired electrons may rearrange for stability.