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Tl Thallium
Element Information, Facts, Properties, Trends, Uses, Comparison with other elements

81
Tl
Thallium
Element 81 of Periodic table is Thallium with atomic number 81, atomic weight 204.3833. Thallium, symbol Tl, has a Simple Hexagonal structure and Silver color. Thallium is a Post Transition Metal element. It is part of group 13 (boron family). Know everything about Thallium Facts, Physical Properties, Chemical Properties, Electronic configuration, Atomic and Crystal Structure.
81 Tl - Thallium | SchoolMyKids

Thallium is a chemical element with symbol Tl and atomic number 81. This soft gray Post Transition Metal is not found free in nature. When isolated, it resembles tin, but discolors when exposed to air.

It belongs to group 13 of the periodic table having trivial name triels, icosagens. It got its trivial name from triels from Greek tri (three, III).

Thallium Facts

Read key information and facts about element Thallium

NameThallium
Atomic Number81
Atomic SymbolTl
Atomic Weight204.3833
PhaseSolid
ColorSilver
Appearancesilvery white
ClassificationPost Transition Metal
Group in Periodic Table13
Group Nameboron family
Period in Periodic Tableperiod 6
Block in Periodic Tablep -block
Electronic Configuration[Xe] 4f14 5d10 6s2 6p1
Electronic Shell Structure (Electrons per shell)2, 8, 18, 32, 18, 3
Melting Point577 K
Boiling Point1746 K
CAS NumberCAS7440-28-0
123456789101112131415161718
1
1
H
Hydrogen
1.008

Atomic #

Electronic Shell #

Symbol
Name
Atomic Weight
HGas
HgLiquid
CSolid
Metals
Metalloids
NonMetals
Alkali metals
Alkali earth metals
Lanthanoids
Transition metals
Post-transition metals
Other nonmetals
Halogens
Nobel gas
Actinoids
2
He
Helium
4.003
2
3
Li
Lithium
6.941
4
Be
Beryllium
9.012
5
B
Boron
10.811
6
C
Carbon
12.011
7
N
Nitrogen
14.007
8
O
Oxygen
15.999
9
F
Fluorine
18.998
10
Ne
Neon
20.180
3
11
Na
Sodium
22.990
12
Mg
Magnesium
24.305
13
Al
Aluminium
26.982
14
Si
Silicon
28.085
15
P
Phosphorus
30.974
16
S
Sulfur
32.065
17
Cl
Chlorine
35.453
18
Ar
Argon
39.948
4
19
K
Potassium
39.098
20
Ca
Calcium
40.078
21
Sc
Scandium
44.956
22
Ti
Titanium
47.867
23
V
Vanadium
50.941
24
Cr
Chromium
51.996
25
Mn
Manganese
54.938
26
Fe
Iron
55.845
27
Co
Cobalt
58.933
28
Ni
Nickel
58.693
29
Cu
Copper
63.546
30
Zn
Zinc
65.409
31
Ga
Gallium
69.723
32
Ge
Germanium
72.640
33
As
Arsenic
74.922
34
Se
Selenium
78.960
35
Br
Bromine
79.904
36
Kr
Krypton
83.798
5
37
Rb
Rubidium
85.468
38
Sr
Strontium
87.620
39
Y
Yttrium
88.906
40
Zr
Zirconium
91.224
41
Nb
Niobium
92.906
42
Mo
Molybdenum
95.940
43
Tc
Technetium
98
44
Ru
Ruthenium
101.070
45
Rh
Rhodium
102.906
46
Pd
Palladium
106.420
47
Ag
Silver
107.868
48
Cd
Cadmium
112.411
49
In
Indium
114.818
50
Sn
Tin
118.710
51
Sb
Antimony
121.760
52
Te
Tellurium
127.600
53
I
Iodine
126.904
54
Xe
Xenon
131.293
6
55
Cs
Cesium
132.905
56
Ba
Barium
137.327
57 - 71
La - Lu
Lanthanides
72
Hf
Hafnium
178.490
73
Ta
Tantalum
180.948
74
W
Tungsten
183.840
75
Re
Rhenium
186.207
76
Os
Osmium
190.230
77
Ir
Iridium
192.217
78
Pt
Platinum
195.078
79
Au
Gold
196.967
80
Hg
Mercury
200.590
81
Tl
Thallium
204.383
82
Pb
Lead
207.200
83
Bi
Bismuth
208.980
84
Po
Polonium
209
85
At
Astatine
210
86
Rn
Radon
222
7
87
Fr
Francium
223
88
Ra
Radium
226
89 - 103
Ac - Lr
Actinides
104
Rf
Rutherfordium
261
105
Db
Dubnium
262
106
Sg
Seaborgium
266
107
Bh
Bohrium
264
108
Hs
Hassium
277
109
Mt
Meitnerium
268
110
Ds
Darmstadtium
281
111
Rg
Roentgenium
272
112
Cn
Copernicium
285
113
Nh
Nihonium
284
114
Fl
Flerovium
289
115
Mc
Moscovium
288
116
Lv
Livermorium
292
117
Ts
Tennessine
294
118
Og
Oganesson
294
Lanthanides
57
La
Lanthanum
138.905
58
Ce
Cerium
140.116
59
Pr
Praseodymium
140.908
60
Nd
Neodymium
144.240
61
Pm
Promethium
145
62
Sm
Samarium
150.360
63
Eu
Europium
151.964
64
Gd
Gadolinium
157.250
65
Tb
Terbium
158.925
66
Dy
Dysprosium
162.500
67
Ho
Holmium
164.930
68
Er
Erbium
167.259
69
Tm
Thulium
168.934
70
Yb
Ytterbium
173.040
71
Lu
Lutetium
174.967
Actinides
89
Ac
Actinium
227
90
Th
Thorium
232.038
91
Pa
Protactinium
231.036
92
U
Uranium
238.029
93
Np
Neptunium
237
94
Pu
Plutonium
244
95
Am
Americium
243
96
Cm
Curium
247
97
Bk
Berkelium
247
98
Cf
Californium
251
99
Es
Einsteinium
252
100
Fm
Fermium
257
101
Md
Mendelevium
258
102
No
Nobelium
259
103
Lr
Lawrencium
262

How to Locate Thallium on Periodic Table

Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 81 to find Thallium on periodic table.

Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Thallium on periodic table look for cross section of group 13 and period 6 in the modern periodic table.

Thallium History

The element Thallium was discovered by W. Crookes in year 1861 in United Kingdom. Thallium was first isolated by C.-A. Lamy in 1862. Thallium derived its name from the Greek thallos, 'green twig'.

Shortly after the discovery of rubidium, Crookes found a new green line in a selenium sample; later that year, Lamy found the element to be metallic.

Thallium Presence: Abundance in Nature and Around Us

The table below shows the abundance of Thallium in Universe, Sun, Meteorites, Earth's Crust, Oceans and Human Body.

 ppb by weight (1ppb =10^-7 %)ppb by atoms (1ppb =10^-7 %)
Abundance in Universe0.50.003
Abundance in Sun10.01
Abundance in Meteorites806
Abundance in Earth's Crust53050
Abundance in Oceans0.0010.000030
Abundance in Humans--

Crystal Structure of Thallium

The solid state structure of Thallium is Simple Hexagonal.

The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.

Unit Cell Parameters

The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a, b and c)

abc
345.66 pm345.66 pm552.48 pm

and the angles between them Lattice Angles (alpha, beta and gamma).

alphabetagamma
π/2 π/2 2 π/3

The positions of the atoms inside the unit cell are described by the set of atomic positions ( xi, yi, zi) measured from a reference lattice point.

The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.

Space Group NameP63/mmc 81 Tl Thallium - Crystal Structure | SchoolMyKids
Oxidation StatesSpace Group Number194
Crystal StructureSimple Hexagonal

Thallium Atomic and Orbital Properties

Thallium atoms have 81 electrons and the electronic shell structure is [2, 8, 18, 32, 18, 3] with Atomic Term Symbol (Quantum Numbers) 2P1/2.

Atomic Number81
Number of Electrons (with no charge)81
Number of Protons81
Mass Number204
Number of Neutrons123
Shell structure (Electrons per energy level)2, 8, 18, 32, 18, 3
Electron Configuration[Xe] 4f14 5d10 6s2 6p1
Valence Electrons6s2 6p1
Valence (Valency)3
Main Oxidation States1, 3
Oxidation States-5, -2, -1, 1, 2, 3
Atomic Term Symbol (Quantum Numbers)2P1/2

Bohr Atomic Model of Thallium - Electrons per energy level

81 Tl Thallium - Electron Shell Structure | SchoolMyKids
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Ground State Electronic Configuration of Thallium - neutral Thallium atom

Abbreviated electronic configuration of Thallium

The ground state abbreviated electronic configuration of Neutral Thallium atom is [Xe] 4f14 5d10 6s2 6p1. The portion of Thallium configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [Xe]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. This is important as it is the Valence electrons 6s2 6p1, electrons in the outermost shell that determine the chemical properties of the element.

Unabbreviated electronic configuration of neutral Thallium

Complete ground state electronic configuration for the Thallium atom, Unabbreviated electronic configuration

1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p1

Electrons are filled in atomic orbitals as per the order determined by the Aufbau principle, Pauli Exclusion Principle and Hund’s Rule.

  • As per the Aufbau principle the electrons will occupy the orbitals having lower energies before occupying higher energy orbitals. According to this principle, electrons are filled in the following order: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p…
  • The Pauli exclusion principle states that a maximum of two electrons, each having opposite spins, can fit in an orbital.
  • Hund's rule states that every orbital in a given subshell is singly occupied by electrons before a second electron is filled in an orbital.
  • Electron configuration of Thallium
    Atomic Structure of Thallium

    Thallium atomic radius is 156 pm, while it's covalent radius is 148 pm.

    Atomic Radius Calculated

    156 pm (1.56 Å)

    Atomic Radius Empirical

    190 pm (1.9 Å)

    Atomic Volume17.24 cm3/mol
    Covalent Radius148 pm (1.48 Å)
    Van der Waals Radius196 pm
    Neutron Cross Section3.4
    Neutron Mass Absorption 0.0006

    Atomic Spectrum of Thallium

    Atomic Spectrum of Thallium | SchoolMyKids

    Thallium Chemical Properties: Thallium Ionization Energies and electron affinity

    The electron affinity of Thallium is 19.2 kJ/mol.

    Valence3
    Electronegativity1.62
    ElectronAffinity19.2 kJ/mol

    Ionization Energy of Thallium

    Refer to table below for Ionization energies of Thallium

    Ionization energy numberEnthalpy - kJ/mol
    1st589.4
    2nd1971
    3rd2878

    Thallium Physical Properties

    Refer to below table for Thallium Physical Properties

    Density11.85 g/cm3(when liquid at m.p density is $11.22 g/cm3)
    Molar Volume17.24 cm3/mol

    Elastic Properties

    Young Modulus8
    Shear Modulus2.8 GPa
    Bulk Modulus 43 GPa
    Poisson Ratio0.45

    Hardness of Thallium - Tests to Measure of Hardness of Element

    Mohs Hardness1.2 MPa
    Vickers Hardness-
    Brinell Hardness26.4 MPa

    Thallium Electrical Properties

    Thallium is Conductor of electricity. Refer to table below for the Electrical properties ofThallium

    Electrical Conductivity6700000 S/m
    Resistivity1.5e-7 m Ω
    Superconducting Point2.38

    Thallium Heat and Conduction Properties

    Thermal Conductivity46 W/(m K)
    Thermal Expansion0.0000299 /K

    Thallium Magnetic Properties

    Magnetic TypeDiamagnetic
    Curie Point-
    Mass Magnetic Susceptibility-3e-9 m3/kg
    Molar Magnetic Susceptibility-6.13e-10 m3/mol
    Volume Magnetic Susceptibility-0.0000356

    Optical Properties of Thallium

    Refractive Index-

    Acoustic Properties of Thallium

    Speed of Sound818 m/s

    Thallium Thermal Properties - Enthalpies and thermodynamics

    Refer to table below for Thermal properties of Thallium

    Melting Point577 K (303.85°C, 578.9300000000001 °F)
    Boiling Point1746 K (1472.85°C, 2683.13 °F)
    Critical Temperature-
    Superconducting Point2.38

    Enthalpies of Thallium

    Heat of Fusion4.2 kJ/mol
    Heat of Vaporization165 kJ/mol
    Heat of Combustion-

    Thallium Isotopes - Nuclear Properties of Thallium

    Thallium has 37 isotopes, with between 176 and 212 nucleons. Thallium has 2 stable naturally occuring isotopes.

    Isotopes of Thallium - Naturally occurring stable Isotopes: 203Tl, 205Tl.

    IsotopeZNIsotope Mass% AbundanceT halfDecay Mode
    176Tl8195176Synthetic
    177Tl8196177Synthetic
    178Tl8197178Synthetic
    179Tl8198179Synthetic
    180Tl8199180Synthetic
    181Tl81100181Synthetic
    182Tl81101182Synthetic
    183Tl81102183Synthetic
    184Tl81103184Synthetic
    185Tl81104185Synthetic
    186Tl81105186Synthetic
    187Tl81106187Synthetic
    188Tl81107188Synthetic
    189Tl81108189Synthetic
    190Tl81109190Synthetic
    191Tl81110191Synthetic
    192Tl81111192Synthetic
    193Tl81112193Synthetic
    194Tl81113194Synthetic
    195Tl81114195Synthetic
    196Tl81115196Synthetic
    197Tl81116197Synthetic
    198Tl81117198Synthetic
    199Tl81118199Synthetic
    200Tl81119200Synthetic
    201Tl81120201Synthetic
    202Tl81121202Synthetic
    203Tl8112220329.524%StableN/A
    204Tl81123204SyntheticStable
    205Tl8112420570.476%StableN/A
    206Tl81125206Synthetic
    207Tl81126207Synthetic
    208Tl81127208Synthetic
    209Tl81128209Synthetic
    210Tl81129210Synthetic
    211Tl81130211Synthetic
    212Tl81131212Synthetic

    Regulatory and Health - Health and Safety Parameters and Guidelines

    Database Search

    List of unique identifiers to search the element in various chemical registry databases

    DatabaseIdentifier number
    CAS Number - Chemical Abstracts Service (CAS)CAS7440-28-0
    RTECS NumberRTECSXG3425000
    CID Number CID5359464
    Gmelin Number-
    NSC Number-