Timeline of chemical element discoveries Modern discoveries Modern discoveries

| Z | Element_ | Observed_or_predicted | Isolated_widely_known | Observer | First_isolator | Notes_ |
|---|---|---|---|---|---|---|
| 58 | Cerium | 1803 | 1839 | H. Klaproth, J. Berzelius, and W. Hisinger | G. Mosander | Berzelius and Hisinger discovered the element in ceria and named it after the newly discovered asteroid (then considered a planet), Ceres. Klaproth discovered it simultaneously and independently in some tantalum samples. Mosander proved later that the samples of all three researchers had at least another element in them, lanthanum. |
| 76 | Osmium | 1803 | 1803 | S. Tennant | S. Tennant | Tennant had been working on samples of South American platinum in parallel with Wollaston and discovered two new elements, which he named osmium and iridium. |
| 77 | Iridium | 1803 | 1803 | S. Tennant | S. Tennant | Tennant had been working on samples of South American platinum in parallel with Wollaston and discovered two new elements, which he named osmium and iridium, and published the iridium results in 1804. |
| 45 | Rhodium | 1804 | 1804 | H. Wollaston | H. Wollaston | Wollaston discovered and isolated it from crude platinum samples from South America. |