Periodic Table Guide
Thorium (Th) has atomic number 90 and is classified as a actinide. It sits in f-block series, period 7 of the periodic table. Its practical relevance includes nuclear-fuel research, high-temperature alloys and historical gas-mantle applications.
Quick facts
Position in the periodic table
Actinides are radioactive f-block metals. Their importance is concentrated in nuclear energy, isotope technology and fundamental research, with radiological protection and material containment central to their handling.
Thorium belongs to period 7. Its position helps explain recurring trends such as atomic size, bonding behavior, oxidation states and the way it interacts with neighboring elements.
Why Thorium matters
In engineering and technology, thorium is associated with nuclear-fuel research, high-temperature alloys and historical gas-mantle applications. The importance of the element may come from the pure element itself, from compounds containing it, or from its role as an alloying, electronic, catalytic or nuclear material.
Engineering and scientific context
Material behavior should never be inferred from the element name alone. Purity, isotope composition, crystal structure, processing history, temperature and the surrounding chemical environment can all change performance. In alloys and compounds, the contribution of thorium depends on concentration and interaction with the other constituents.
Safety and handling
Thorium is radioactive, so any practical work involving it requires specialist radiological controls, approved facilities and isotope-specific procedures.
Related elements
Actinium (Ac) · Protactinium (Pa)
Reference sources
For authoritative element data and current standard atomic-weight guidance, consult the Royal Society of Chemistry Periodic Table and the IUPAC Periodic Table of the Elements.
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