Symbol
Tl
Atomic Number
81
Atomic Mass
204.38
Protons
81
Neutrons
123
Electrons
81
Type
Post-Transition Metal
Isotopes
Thallium-203, Thallium-204, Thallium-205
Discovery Year
1861
Discovered By
William Crookes
Group
13
Period
6
Boiling Point
1450°C
Melting Point
304°C
Electron Configuration
[Xe] 6s² 4f¹⁴ 5d¹⁰ 6p¹
Density (g/cm³)
11.85
Crystal Structure
Rhombohedral
Magnetism
Diamagnetic
Abundance in Earth's Crust
0.0005%
Phase at Room Temperature
Solid