Advanced Topic 685 of 1102 Inorganic Chemistry
Actinides
Radioactive elements from actinium to lawrencium, including uranium and plutonium.
In-depth explanation of Actinides
The actinides are the fifteen elements from actinium to lawrencium, atomic numbers 89 to 103, in which the 5f subshell is progressively filled. All are radioactive, and the heavier ones are made only artificially. Unlike the 4f electrons of the lanthanides, the 5f orbitals are more extended and take part in bonding, so the actinides show a wider range of oxidation states, reaching +7 for neptunium and plutonium. Uranium and plutonium are the most important, being used as nuclear fuel and in weapons. Their chemistry is complicated by radioactivity and toxicity.
Going deeper: Actinides
Key ideas: Elements Th to Lr with 5f filling. Show more oxidation states than lanthanides (U: +3 to +6; Np, Pu up to +7) because 5f, 6d and 7s energies are close. Radioactive; the actinide contraction also exists but is larger as 5f shielding is poorer. Uranium isotopes: U-235 (0.72 percent natural) is fissile; U-238 can breed Pu-239. Uranium is enriched by gaseous diffusion or centrifuge of UF6. Elements beyond U are made artificially.
Common mistakes and connections: Students think all actinides are naturally occurring; only Th and U (traces of Pa, Pu, Np) occur. Radiation is nuclear, not chemical, so chemistry cannot stop decay. Do not confuse enrichment with chemical separation; isotopes are separated by mass. Links to nuclear chemistry, half-life, lanthanides and nuclear waste.
Visualization of Actinides
Radioactive decay of an actinide: an unstable nucleus loses activity exponentially with its half-life, and every actinide is radioactive. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Uranium-235 fissions when it captures a slow neutron, releasing energy and additional neutrons.
Frequently asked questions about Actinides
What is Actinides?
Radioactive elements from actinium to lawrencium, including uranium and plutonium.
Is Actinides a beginner, intermediate or advanced topic?
Actinides is a advanced topic in Inorganic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Actinides?
Study these earlier topics in Inorganic Chemistry first: Gold and Platinum, Mercury, Lanthanides.
What comes after Actinides?
The next topics in Inorganic Chemistry are Superheavy Elements and Metallurgy.
Can I practise Actinides with quizzes?
Yes. The interactive lesson includes a self-check question on Actinides, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Actinides fits in Inorganic Chemistry
Actinides is topic 70 of 113 in Inorganic Chemistry.