Return to the Main CHEMystery Page.
Return to the Periodic Table of the Elements

Element 81 - Thallium (Tl) sound

From thallos, or a young shoot--its spectrum is a bright-green line; discovered in 1861. Its chief use in in thallium sulfate--a deadly rat poison. Odorless and tasteless, it is mixed with starch, sugar, glycerine, and water to make an inviting if ominous "treat" for household rodents.

Properties

Atomic Number: 81
Atomic Weight: 204.383
Electron Configuration (at ground state): 1s22s22p63s23p63d104s24p64d104f145s25p65d106s26p1
Oxidation States (Bold most stable): +3, +1
Boiling Point (K): 1746
Melting Point (K): 577
Density (at 300K -- g/cm3): 11.85
Atomic Volume (at 300K -- cm3/mol) 17.20
Number of stable isotopes: 2
Number of natural radioactive isotopes: 4
Mass Number (Bold naturally occurring) -- Half-Life -- Disintigration Type: 204 -- 3.77 years -- beta particle (electron) emission
Covalent Radius (Å): 1.48
Atomic Radius (Å): 1.71
First Ionization Potential (V): 6.108
Electronegativity (Pauling's): 2.04
Specific Heat Capacity (at 300K -- J g-1 K-1): 0.129
Heat of Vaporization (kJ/mol): 162.09
Heat of Fusion (kJ/mol): 4.27
Electrical Conductivity (at 293K for polycrystalline material -- 106 (ohms)-1 cm-1): 5.6
Thermal Conductivity (at 300K -- W m-1 K-1): 46.1
Crystal Structure: Hexagonal
Acid-Base Properties: Very basic