Periodic Table
Overview
Classification of elements by atomic number Z and electron configuration. Periodicity in properties emerges from shell structure. Mendeleev (1869) predicted unknown elements from gaps.
Era: 1869
Proposed at: Saint Petersburg, Russia
Formal structure
Domain: Element E, Z ∈ ℕ, electron configuration (n, ℓ, m, s)
E(Z) ↦ (properties); period = row, group = column
Constraints: Pauli exclusion: at most 2 electrons per (n, ℓ, m); Hund rules
Objective: Predict chemical behavior from position in table