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Overview

Thallium is a member of the aluminum family, Group 13 (IIIA) on the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. Thallium is also a member of the heavy metals, along with gold, platinum, and lead.

Thallium was first discovered by means of a spectroscope. A spectroscope is a device for analyzing the light produced when an element is heated. The spectrum (plural: spectra) of an element consists of a series of colored lines that are different for every element. The brightest lines in the spectrum of thallium are green, which accounts for its name. In Greek, the word thallos means "green twig." The green lines in thallium's spectrum look like green twigs.