Atomic Number: 81

Atomic Weight: 204.3833

Melting Point: 577 K (304°C or 579°F)

Boiling Point: 1746 K (1473°C or 2683°F)

Density: 11.8 grams per cubic centimeter

Phase at Room Temperature: Solid

Element Classification: Metal

Period Number: 6

Group Number: 13

Group Name: none

Thallium has two stable isotopes and one of these, Tl-203, is used to produce one of the ₍workhorses⁽ of nuclear medicine: Tl-201. Tl-201 is used extensively for imaging and in particular for perfusion tests of the myocardium. These tests are done to determine the damage to the heart from a heart attack or from heart diseases. Tl205 has been proposed as an alternative target for the production of Tl-201. Tl-205 is also used in nuclear magnetic resonance research.