Chemistry study notes
Atomic Structure
Count particles, build electron configurations and read the evidence in ionisation energies.
A-Level 9476 (2026-2027)
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4 topicsParticles, isotopes and electric fields
Connect mass and charge to particle counts and beam paths.
Orbitals and their energies
What s, p and d orbitals mean, how many there are, and their shapes.
Writing electron configurations
Fill orbitals, account for exceptions and remove the correct electrons from ions.
Ionisation energies as evidence
Explain an energy change and use large jumps to reconstruct an atom.
Scope
Learning outcomes
1. Atomic Structure. Use the outcome map to find the explanation for a particular syllabus requirement.
See the learning outcome map
1(a) Describe the three subatomic particles.
- Relative proton, neutron and electron charges
- Relative masses
1(b) Deduce particle-beam behaviour in an electric field.
- Proton, neutron and electron beam directions
- Mass and charge comparisons under stated speed conditions
1(c) Locate the mass and charges of an atom.
- Concentrated nuclear mass and positive charge
- Negative electrons outside the nucleus
1(d) Calculate particle counts in atoms and ions.
- Proton and nucleon numbers
- Positive and negative ion charges
1(e) Explain nuclear composition and isotopes.
- (i) Proton number and nucleon number
- (ii) Same protons, different neutron counts in isotopes
1(f) Describe orbital numbers and relative energies.
- s, p and d subshells for n = 1, 2, 3
- 4s and 4p
- One, three and five orbitals in s, p and d
1(g) Recognise s, p and d orbital shapes.
- Spherical s
- Three two-lobed p orientations
- Five d orbitals including dz2
- No wave-function mathematics
1(h) Write configurations of atoms and ions.
- Proton number and charge
- Orbital filling and electron pairing
- Cr and Cu; 4s removal in transition-metal ions
1(i) Explain ionisation-energy differences.
- Nuclear attraction, shielding, distance
- Subshell energy and paired-electron repulsion
- Data Booklet and periodic trends
1(j) Deduce configurations from successive ionisation energies.
- Increasing positive charge
- Large jumps and shell boundaries
- Combining energy evidence with particle count or period
1(k) Link successive ionisation energies to periodic position.
- Main-group outer-electron count
- Group inference
- Limits on identifying a period from a partial succession