元素週期表

定義與不確定度

原子量

mass is a legacy numeric display field. Read atomicWeight.kind before interpreting it: abridged standard atomic weights describe terrestrial isotope mixtures, while bracketed entries name a representative isotope and are not atomic weights.

代表同位素

A is an explicitly selected isotope mass number, not a rounded atomic weight. Stable elements use the most abundant terrestrial isotope; radioactive elements use the isotope represented by this dataset or its half-life entry.

豐度

crust is an approximate bulk continental-crust concentration in ppm by mass. solar is the Asplund et al. (2021) present-day photospheric log epsilon value (or an explicitly marked meteoritic proxy), normalized to log epsilon(H)=12; it is neither ppm nor generic Solar-System abundance.

地殼與海水儲庫

crustAbundance targets bulk continental crust on a mass basis; seawaterAbundance targets representative surface seawater as dissolved-element-equivalent mg/L. Both are heterogeneous reservoirs. A null range means this dataset has not encoded a defensible range, not that the value is spatially constant.

離子半徑

Ionic radii are Shannon effective radii for a specified ion and coordination context. They are not free-ion sizes. Compare only the same charge, coordination number and spin state; missing coordination or spin metadata blocks a defensible trend comparison.

大氣

Atmospheric entries are species-specific. Gases use mole fraction in ppmv; aerosols use mass concentration in ug/m3 and must not be compared directly. Dry-air values exclude water vapour. CO2 is NOAA's provisional March 2026 global monthly marine-surface mean.

核合成與天然存在

origin is retained as a single educational display category. nucleosynthesis stores multiple production channels and uncertainty; occurrence separately describes terrestrial presence and must not be read as a production mechanism.

地球化學

Goldschmidt affinities are simplified first-order tendencies. Partitioning varies with oxidation state, pressure, temperature, mineral assemblage and planetary differentiation.

電子親和力

Electron affinity is for an isolated neutral gas-phase atom. not-established includes unstable/unbound anions and missing recommended values; estimated values should not be used as equal-quality trend points.

量測條件

Phase, density, melting and boiling values are educational reference values near standard pressure unless noted; allotropy and sublimation can make a single value misleading.

生物與毒理脈絡

Biological and medical effects belong to particular organisms, chemical species, isotope, route and dose. `toxic: false` means not flagged by this compact dataset, never safe. Dose thresholds are intentionally null until a route- and species-specific source is encoded.

關鍵礦物政策

Critical-mineral status is not intrinsic to an element. criticalMineral maps elements to commodity names on the final U.S. USGS 2025 list, with jurisdiction, version and date; the boolean critical field is only a compatibility projection.

區塊分類慣例

blockOf uses the conventional displayed periodic-table region: the detached lanthanide and actinide series, including Lr, are f-block. Lr's accepted ground-state configuration ends in 7p1, so a literal last-subshell convention would call it p-block instead.