Timeline of chemical element discoveries Modern discoveries Modern discoveries

| Z | Element_ | Observed_or_predicted | Isolated_widely_known | Observer | First_isolator | Notes_ |
|---|---|---|---|---|---|---|
| 88 | Radium | 1898 | 1902 | P. and M. Curie | M. Curie | The Curies reported on December 26, 1898, a new element different from polonium, which Marie later isolated from uraninite. |
| 86 | Radon | 1898 | 1910 | E. Dorn | W. Ramsay and R. Whytlaw-Gray | Dorn discovered a radioactive gas resulting from the radioactive decay of radium, isolated later by Ramsay and Gray. |
| 89 | Actinium | 1899 | 1899 | A.-L. Debierne | A.-L. Debierne | Debierne obtained from pitchblende a substance that had properties similar to those of thorium. |
| 63 | Europium | 1896 | 1901 | E.-A. Demarçay | E.-A. Demarçay | Demarçay found spectral lines of a new element in Lecoq`s samarium, and separated this element several years later. |