Thallium (Tl)
Thallium (Tl, element 81) is a post-transition metal in group 13, period 6. Atomic mass 204.383, electron configuration [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹, uses and…
About Thallium
Thallium is a post-transition metal with the symbol Tl and atomic number 81. It is a solid at room temperature, and it sits in group 13, period 6 of the periodic table. Thallium was discovered in 1861 by William Crookes.
Thallium key facts
- Atomic number: 81
- Symbol: Tl
- Atomic mass: 204.383 u
- Category: post-transition metal
- Group: 13
- Period: 6
- State at room temperature: solid
- Electron configuration: [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹
- Electronegativity (Pauling): 1.62
- Melting point: 577 K (303.85 °C)
- Boiling point: 1746 K (1472.85 °C)
- Density: 11.85 g/cm³
- Common oxidation states: +1, +3
Electron configuration
The electron configuration of thallium is [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹. The part in brackets is the noble gas core; the rest shows how the outer electrons fill their subshells. Thallium has 3 valence electrons.
Uses of thallium
- Electronics
- Infrared detectors
- Historical: rat poison
Did you know?
Thallium poisoning was used in many Cold War assassination plots, it causes hair loss and nerve damage.
Other elements in group 13 and neighbours
Frequently asked questions
What is the atomic number of thallium?
The atomic number of thallium is 81, which means every thallium atom has 81 protons.
What is the electron configuration of thallium?
The electron configuration of thallium is [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹.
What group and period is thallium in?
Thallium is a post-transition metal in group 13, period 6.
What state is thallium at room temperature?
Thallium is a solid at room temperature.
What is thallium used for?
Thallium is used for electronics, infrared detectors, historical: rat poison.