Chapter summary
Atomic Structure, at a glance
Count particles, build electron configurations and read the evidence in ionisation energies.
A-Level 9476 (2026-2027)
Quick revision
Revisit the essentials, then return to an explanation when you need it.
| Task | Reliable starting point |
|---|---|
| Count particles | p = Z; n = A - Z; e = Z - signed charge. |
| Compare deflection | Direction follows charge. At equal speed and field, compare |q|/m. |
| Count orbital capacity | s: 1 orbital/2 e; p: 3/6; d: 5/10. |
| Form transition-metal cations | Write the neutral configuration, then remove 4s before 3d. |
| Explain first IE | Compare nuclear charge, shielding, distance, subshell and pairing. |
| Read successive IE | A large jump indicates inner-shell removal; count electrons before it. |
Keep the distinctions: isotope versus ion; orbital versus subshell; electron count versus proton number; filling order versus removal order; general periodic trend versus a subshell or pairing exception.