Elements
81

Tl

Thallium

Thallium (Tl) is a soft gray metal that has the atomic number 81 in the periodic table in Group 13. It has the symbol Tl.

Thallium was discovered in 1861 by William Crookes> he had been given an ore containing selenium which he extracted leaving behind tellurium. Eleven years later he tried to isolate tellurium again but instead through analysis with spectroscopy realised he had isolated a completely new element. Thalium was named after the Greek word ‘Thallos’ which means green shoot, in reference to its unique green line. Thallium is a highly toxic compound and was used in the Agatha Christie novel ‘the pale horse.’ Thallium is used in rat poison and insecticide and also used to make photovoltaic cells. It is a solid metal at room temperature with a melting point of 304°c and a boiling point of 1473°c.

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FAQ's

What is the Melting Point for Thallium?

Thallium has a Melting Point of 303.5°F, meaning at 303.5°F it will turn to a liquid.

What is the Boiling Point for Thallium?

Thallium has a Boiling Point of 1457°F, meaning at 1457°F it will turn to a Gas.

What is the Electronegativity of Thallium?

Thallium's Electronegativty is 1.62. Electronegativity is a measure of how strongly atoms attract bonding electrons to themselves.

What is the Heat of Vaporization of Thallium?

Thallium has a Heat of Vaporization of 164.1 kJ/mol.

Uses

Its compounds are used in rat and ant poisons. Also for detecting infrared radiation.

Sources

Found in iron pyrites. Also in crookesite, hutchinsonite and lorandite. Most is recovered from the byproducts of lead and zinc refining.

81
Protons
81
Electrons
123
Neutrons

Tl

Element Symbol
Tl
Atomic Weight
204.38
Atomic Number
81
State
Solid
Melting Point
Unknown
303.5
°C
Boiling Point
1457
Unknown
°C
Heat of Vaporization
164.1
Unknown
kJ/mol
Crystal Structure
Hexagonal
Thermoconductivity
0.461
Unknown
W/cmK
Shells
2,8,18,32,18,3
Group
Post-Transition Metal
Period
6
Block
P Block
Orbitals
[Xe] 4f14 5d10 6s2 6p1
Coefficient of Thermal Expansion
29.9 10^-6 K^-1
Covalent Radius
1.48 Å
Density at 293K
11.85 g/cm³
Electrical Conductivity
0.0617 10^6/cm ohm
First Ionization Potential
6.1083 V
Second Ionization Potential
20.428 V
Third Ionization Potential
29.829 V
Ionic Radius
1.59 (+1) Å
Oxydation States
3,(1)
Lattice Parameter
3.4567 Å
Lattice Parameter 2
--
Lattice Parameter 3
--
Pronounced

THAL-i-em

Discovered by

Sir William Crookes

Discovery date

1861

Orbital configuration
2,8,18,32,18,3

Download the Periodic Table

Explore Other Post-Transition Metals

208.98
83

Bi

Bismuth
26.982
13

Al

Aluminium
209
84

Po

Polonium
69.723
31

Ga

Gallium
118.71
50

Sn

Tin
114.818
49

In

Indium
207.2
82

Pb

Lead
The post-transition metals are the ones found between the transition metals (to the left) and the metalloids (to the right). They include aluminium (Al), gallium (Ga), indium (In), thallium (Tl), tin (Sn), lead (Pb) and bismuth (Bi).
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