81
Tl
204.38
Thallium (Tl)
Element 81 · Period 6 · Group 13
post-transition
solid at room temp
p-block
About Thallium
Highly toxic. Used in electronics and in detecting radiation.
Physical Properties
Atomic Mass
204.38 u
State at 25°C
Solid
Melting Point
304 °C
Boiling Point
1473 °C
Density
11.85 g/cm³
Magnetism
Diamagnetic
Atomic Properties
Electron Configuration
[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹
Electron Shells
2, 8, 18, 32, 18, 3
Electronegativity
1.62
Atomic Radius
156 pm
Ionization Energy
589 kJ/mol
Oxidation States
+1, +3
Discovery & History
Discovered By
William Crookes
Discovery Year
1861
Named By
William Crookes
Name origin: Greek: thallos (green shoot)
Frequently Asked Questions
- Is Thallium a metal, nonmetal, or metalloid?
- Thallium is classified as a post-transition.
- What state is Thallium in at room temperature?
- Thallium is a solid at standard room temperature (25°C).
- What is the atomic mass of Thallium?
- Thallium has an atomic mass of 204.38 atomic mass units (u).
- Who discovered Thallium?
- Thallium was discovered by William Crookes in 1861.
- Where is Thallium on the periodic table?
- Thallium is element number 81, located in period 6 and group 13.