Radioactive elements of the f-block
Actinides are 15 chemical elements with atomic numbers from 89 (actinium) to 103 (lawrencium). All actinides are radioactive. Thorium and uranium occur in nature, the rest are synthetic. They are important for nuclear energy and weapons.
Read in glossary1 kg of uranium-235 releases energy equivalent to 3000 tons of coal
Plutonium-238 has powered Voyager spacecraft for over 45 years
Elements after uranium are named after planets: Neptunium, Plutonium
Marie Curie died from anemia caused by working with radium
Americium is used in household smoke detectors
Actinides are characterized by filling of 5f orbitals. Their general configuration is [Rn]5f¹⁻¹⁴6d⁰⁻¹7s². Unlike lanthanides, 5f electrons are less shielded and more actively participate in chemical bonds.
Actinides are reactive metals. They react with water, acids, and oxygen. They have more diverse oxidation states compared to lanthanides (from +2 to +7).
| Element | Z | Mass u | M.P. °C | B.P. °C | ρ г/см³ | EN |
|---|---|---|---|---|---|---|
Ac Actinium | 89 | 227.03 ▼ | 1050 | 3200 | 10.07 | 1.10 ▼ |
Th Thorium | 90 | 232.04 | 1750 ▲ | 4788 ▲ | 11.72 | 1.30 |
Pa Protactinium | 91 | 231.04 | 1572 | 4027 | 15.37 | 1.50 ▲ |
U Uranium | 92 | 238.03 | 1135 | 4131 | 18.95 | 1.38 |
Np Neptunium | 93 | 237.05 | 644 | 3902 | 20.25 ▲ | 1.36 |
Pu Plutonium | 94 | 244.06 | 639 ▼ | 3228 | 19.82 | 1.28 |
Am Americium | 95 | 243.06 | 1176 | 2011 | 13.69 | 1.30 |
Cm Curium | 96 | 247.07 | 1345 | 3127 | 13.51 | 1.30 |
Bk Berkelium | 97 | 247.07 | 1050 | 2627 | 14.00 | 1.30 |
Cf Californium | 98 | 251.08 | 900 | 1470 | 15.10 | 1.30 |
Es Einsteinium | 99 | 252.08 | 860 | 996 ▼ | 8.84 ▼ | 1.30 |
Fm Fermium | 100 | 257.10 | 1527 | — | — | 1.30 |
Md Mendelevium | 101 | 258.10 | 827 | — | — | 1.30 |
No Nobelium | 102 | 259.10 | 827 | — | — | 1.30 |
Lr Lawrencium | 103 | 266.12 ▲ | 1627 | — | — | 1.30 |
The name 'actinides' comes from actinium (Greek ἀκτίς, aktis — 'ray'). Actinium was named for its radioactivity. Elements after uranium are called 'transuranium' — they don't exist in nature.
Martin Klaproth discovered uranium, naming it after planet Uranus
Hahn and Strassmann discovered uranium nucleus fission
Enrico Fermi started the first nuclear reactor in Chicago
First nuclear bombs (uranium and plutonium) changed the world
Synthesized plutonium and 9 other transuranium elements, Nobel Prize 1951
Created the first nuclear reactor, Nobel Prize 1938
Discovered nuclear fission of uranium, Nobel Prize 1944