> **PROTOTYPE:** a suggestion, not an official CIAAW or IUPAC page. Official values are at [ciaaw.org](https://ciaaw.org).

# Comparison: Wikidata atomic weights

Standard atomic weights in this data compared with the mass (P2067, in dalton) of the chemical elements in [Wikidata](https://www.wikidata.org), matched on the atomic number. A weight agrees if the Wikidata value is inside the local interval or within the local uncertainty, or if the bounds of a rounded Wikidata value contain the local weight. The comparison is made by `check_wikidata_weights.py`.

Compared on 2026-11-05: 84 elements in `ciaaw.ttl`, 174 items in Wikidata.

| Result | Count |
| --- | --- |
| Different values | 0 |
| No value | 0 |
| Not found | 0 |
| Unexpected unit | 0 |
| Only in the resource | 34 |

## Only in the resource

Wikidata has a mass for the element, the local data has no standard atomic weight for it. CIAAW gives none for these elements (no stable isotopes, or not assessed).

| Element | Local | Value in resource | Item | Source |
| --- | --- | --- | --- | --- |
| technetium | — | 97.907 | [Q1054](https://www.wikidata.org/wiki/Q1054) | [PubChem](https://www.wikidata.org/wiki/Q278487) |
| promethium | — | 144.9127559 [144.9127526, 144.9127592] | [Q1809](https://www.wikidata.org/wiki/Q1809) | — |
| polonium | — | 208.9824308 [208.9824288, 208.9824328] | [Q979](https://www.wikidata.org/wiki/Q979) | — |
| astatine | — | 209.9871479 [209.9871396, 209.9871562] | [Q999](https://www.wikidata.org/wiki/Q999) | — |
| radon | — | 222.0175782 [222.0175757, 222.0175807] | [Q1133](https://www.wikidata.org/wiki/Q1133) | — |
| francium | — | 223.019736 [223.0197335, 223.0197385] | [Q671](https://www.wikidata.org/wiki/Q671) | — |
| radium | — | 226.0254103 [226.0254078, 226.0254128] | [Q1128](https://www.wikidata.org/wiki/Q1128) | — |
| actinium | — | 227.028 | [Q1121](https://www.wikidata.org/wiki/Q1121) | [PubChem](https://www.wikidata.org/wiki/Q278487) |
| neptunium | — | 237.0481736 [237.0481717, 237.0481755] | [Q1105](https://www.wikidata.org/wiki/Q1105) | — |
| plutonium | — | 244.0642053 [244.0641997, 244.0642109] | [Q1102](https://www.wikidata.org/wiki/Q1102) | — |
| americium | — | 243 | [Q1872](https://www.wikidata.org/wiki/Q1872) | [RCSB protein data bank](https://www.wikidata.org/wiki/Q55823721) |
| curium | — | 247.07 | [Q1876](https://www.wikidata.org/wiki/Q1876) | [PubChem](https://www.wikidata.org/wiki/Q278487) |
| berkelium | — | 247.0703073 [247.0703014, 247.0703132] | [Q1882](https://www.wikidata.org/wiki/Q1882) | — |
| californium | — | 251.0795886 [251.0795838, 251.0795934] | [Q1888](https://www.wikidata.org/wiki/Q1888) | — |
| einsteinium | — | 252.08298 [252.082926, 252.083034] | [Q1892](https://www.wikidata.org/wiki/Q1892) | — |
| fermium | — | 257.095 | [Q1896](https://www.wikidata.org/wiki/Q1896) | [PubChem](https://www.wikidata.org/wiki/Q278487) |
| mendelevium | — | 258.0984315 [258.0984265, 258.0984365] | [Q1898](https://www.wikidata.org/wiki/Q1898) | — |
| nobelium | — | 259.10103 [259.10092, 259.10114] | [Q1901](https://www.wikidata.org/wiki/Q1901) | — |
| lawrencium | — | 266.11983 [266.11927, 266.12039] | [Q1905](https://www.wikidata.org/wiki/Q1905) | — |
| rutherfordium | — | 267.12179 [267.12117, 267.12241] | [Q1226](https://www.wikidata.org/wiki/Q1226) | — |
| dubnium | — | 268.12567 [268.1251, 268.12624] | [Q1232](https://www.wikidata.org/wiki/Q1232) | — |
| seaborgium | — | 267.12436 [267.12406, 267.12466] | [Q1234](https://www.wikidata.org/wiki/Q1234) | — |
| bohrium | — | 270.13336 [270.13305, 270.13367] | [Q1249](https://www.wikidata.org/wiki/Q1249) | — |
| hassium | — | 271.13717 [271.13685, 271.13749] | [Q1252](https://www.wikidata.org/wiki/Q1252) | — |
| meitnerium | — | 278.15631 [278.15563, 278.15699] | [Q1258](https://www.wikidata.org/wiki/Q1258) | — |
| darmstadtium | — | 281.16451 [281.16392, 281.1651] | [Q1266](https://www.wikidata.org/wiki/Q1266) | — |
| roentgenium | — | 282.16912 [282.1684, 282.16984] | [Q1272](https://www.wikidata.org/wiki/Q1272) | — |
| copernicium | — | 285.17712 [285.17652, 285.17772] | [Q1278](https://www.wikidata.org/wiki/Q1278) | — |
| nihonium | — | 286.18221 [286.18149, 286.18293] | [Q1301](https://www.wikidata.org/wiki/Q1301) | — |
| flerovium | — | 289.191 | [Q1302](https://www.wikidata.org/wiki/Q1302) | — |
| moscovium | — | 290.19598 [290.19525, 290.19671] | [Q1303](https://www.wikidata.org/wiki/Q1303) | — |
| livermorium | — | 293.20449 [293.20389, 293.20509] | [Q1304](https://www.wikidata.org/wiki/Q1304) | — |
| tennessine | — | 294.21046 [294.20972, 294.2112] | [Q1306](https://www.wikidata.org/wiki/Q1306) | — |
| oganesson | — | 294.21392 [294.21321, 294.21463] | [Q1307](https://www.wikidata.org/wiki/Q1307) | — |