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Thallium (Tl)
Element with atomic number 81, category: Post-transition metal, a solid at room temperature.
Element 81 of 118
Post-transition metal
Thallium
Group 13, Period 6
Common Uses
Electronics (toxic)
Electron Diagram
About Thallium
Thallium is a chemical element with the symbol Tl and atomic number 81, meaning every atom has 81 protons in its nucleus. It is classed as Post-transition metal and is a solid at room temperature. Its atomic mass is about 204.38 atomic mass units (u).
On the periodic table, Thallium sits in group 13, period 6, which determines how many electron shells it has and how it tends to react with other elements.
Uses of Thallium
In daily life and industry, Thallium is used for Electronics (toxic). These uses are closely tied to the typical properties of elements in the Post-transition metal category.
Electron Structure of Thallium
Using a simplified electron shell model (at most 2 electrons in the first shell, 8 in the second, 18 in the third, and so on), Thallium has 5 electron shells, with an approximate arrangement of 2, 8, 18, 32, 21 electrons from the innermost shell to the outermost. This is a simplified learning model, not the full electron configuration that accounts for the s, p, d and f subshells.
Explore Other Elements
Want to see another element or try the element symbol quiz? Go back to the Interactive Periodic Table to explore all 118 chemical elements.