81Tl
Element 81
Thallium
Post-transition metals
Thallium is a chemical element with symbol Tl and atomic number 81.
Key data
- Atomic number
- 81
- Atomic mass
- 204.380 u
- Group / Period
- 13 / 6
- Block
- p-block
- Phase at STP
- Solid
- Density
- 11.85 g/cm³
- Melting point
- 303.9 °C
- Boiling point
- 1472.8 °C
- Electron configuration
- [Xe] 4f14 5d10 6s2 6p1
Common uses
- •Rat poison (banned)
- •Infrared detectors
- •Heart imaging
Discovery
Year: 1861
Discovered by: William Crookes
Frequently asked questions
What is the atomic number of Thallium?
Thallium has atomic number 81. Its symbol is Tl and its atomic mass is 204.38 u.
What category of element is Thallium?
Thallium is classified as post-transition metals. It sits in group 13, period 6 of the periodic table.
What is Thallium used for?
Common uses of Thallium include: Rat poison (banned), Infrared detectors, Heart imaging.
When was Thallium discovered?
Thallium was discovered in 1861 by William Crookes.
Play the game
Test your knowledge in The Lab
20-round element ID, cryptic 3-clue guesser, and an interactive periodic table.
Open The Lab →