Thallium (Tl)

Thallium is the 81st element in the periodic table and has a symbol of Tl and atomic number of 81. It has an atomic weight of 204.380 and a mass number of 205. Thallium has eighty-one protons and one hundred twenty-four neutrons in its nucleus, and eighty-one electrons in six shells. It is located in group thirteen, period six and block p of the periodic table. Pure, unreacted thallium appears silvery-white and exhibits a metallic lustre. Upon reacting with air, it begins to turn bluish-grey and looks like lead. It is very malleable, and can be cut with a knife. There are two stable isotopes, and four radioisotopes, Tl-204 being the most stable with a half-life of 3.78 years. Thallium sulphate was used as a rodenticide. Thallium sulphine's conductivity changes with exposure to infrared light, this gives it a use in infrared detectors. Discovered by Sir William Crookes via spectroscopy. Its name comes from the Greek word thallos, which means green twig. Thallium and its compounds are toxic and can cause cancer.

Atomic Number	81
Atomic Weight	204.38
Mass Number	205

Group	13
Period	6
Block	p

Protons	81 p⁺
Neutrons	124 n⁰
Electrons	81 e^-

Properties

Physical Properties
Atomic Radius	190 pm 242 pm
Molar Volume	17.2 cm³/mol
Covalent Radius	144 pm 142 pm 150 pm 190 pm 145 pm
Metallic Radius	144 pm 160 pm
Ionic Radius	150 pm 159 pm 170 pm 75 pm 88.5 pm 98 pm
Crystal Radius	164 pm 173 pm 184 pm 89 pm 102.5 pm 112 pm
Van der Waals Radius	220 pm 196 pm 196 pm 259 pm 434.7 pm
Density	11.8 g/cm³ 11,220 kg/m³
Energy
Proton Affinity
Electron Affinity	0.377 eV/particle
Ionization Energy	6.108287 eV/particle 20.4283 eV/particle 29.852 eV/particle 51.14 eV/particle 62.6 eV/particle 80 eV/particle 98 eV/particle 116 eV/particle 135 eV/particle 158 eV/particle 177 eV/particle 198 eV/particle 218.3 eV/particle 306.9 eV/particle 340 eV/particle 366 eV/particle 392 eV/particle 439 eV/particle 467 eV/particle 520 eV/particle 570 eV/particle 600 eV/particle 640 eV/particle 700 eV/particle 760 eV/particle 820 eV/particle 880 eV/particle 930 eV/particle 990 eV/particle 1,060 eV/particle 1,110 eV/particle 1,170 eV/particle 1,230 eV/particle 1,290 eV/particle 1,350 eV/particle 1,625 eV/particle 1,681 eV/particle 1,740 eV/particle 1,802 eV/particle 1,862 eV/particle 1,920 eV/particle 2,014 eV/particle 2,075 eV/particle 2,140 eV/particle 2,202 eV/particle 2,447 eV/particle 2,508 eV/particle 2,574 eV/particle 2,635 eV/particle 2,854 eV/particle 2,925 eV/particle 3,094 eV/particle 3,164.7 eV/particle 5,234 eV/particle 5,371 eV/particle 5,518 eV/particle 5,674 eV/particle 5,824 eV/particle 5,969 eV/particle 6,241 eV/particle 6,392 eV/particle 6,560 eV/particle 6,714 eV/particle 7,146 eV/particle 7,281 eV/particle 7,430 eV/particle 7,560 eV/particle 8,260 eV/particle 8,420 eV/particle 8,730 eV/particle 8,880 eV/particle 19,070 eV/particle 19,440 eV/particle 19,840 eV/particle 20,210 eV/particle 22,780 eV/particle 23,260 eV/particle 23,850 eV/particle 24,234.1 eV/particle 96,783.2 eV/particle 98,591.6 eV/particle

Heat of Vaporization	162.4 kJ/mol
Heat of Fusion	4.31 kJ/mol
Heat of Formation	182.2 kJ/mol
Electrons
Electron Shells	2, 8, 18, 32, 18, 3

Valence Electrons	3 ⓘ

Electron Configuration	[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹ⓘ 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p¹

Oxidation States	-5, -2, -1, 1, 2, 3
Electronegativity	0.173447 1.8
Electrophilicity Index	0.9173102715055317 eV/particle
States of Matter
Phase	Solid
Gas Phase
Boiling Point	1,746.15 K
Melting Point	577.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Thallium is a Silver. Tl has a CPK of #ff1493, Jmol of #a6544d, and MOLCAS GV of #a6544d. The Appearance of Element 81 is silvery white.
Color	Silver #ff1493 #a6544d #a6544d
Appearance	silvery white
Refractive Index
Thermodynamic Properties
Thermal Conductivity	46.1 W/(m K)
Thermal Expansion	0.0000299 1/K
Molar Heat Capacity	26.32 J/(mol K)
Specific Heat Capacity	0.129 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
Type	Conductor
Electrical Conductivity	6.7 MS/m
Electrical Resistivity	0.00000015 m Ω
Superconducting Point	2.38 K
Magnetism
Type	diamagnetic
Magnetic Susceptibility (Mass)	-0.000000003 m³/Kg
Magnetic Susceptibility (Molar)	-0.000000000613 m³/mol
Magnetic Susceptibility (Volume)	-0.0000356
Magnetic Ordering
Curie Point
Neel Point
Structure
The Crystal Structure of Thallium is HEX. The lattice constant of Tl is 3.46 Å. The lattice angles of Element 81 are π/2, π/2, 2 π/3.
Crystal Structure	Simple Hexagonal (HEX)
Lattice Constant	3.46 Å
Lattice Angles	π/2, π/2, 2 π/3
Mechanical Properties
Thallium has a Brinell of 26.4 MPa, and Mohs hardness of 1.2 MPa. The Bulk Modulus of Tl is 43 GPa. The Shear Modulus of Element 81 is 2.8 GPa. The Young Modulus of Thallium (Tl) is 8 GPa. The Poisson Ratio of Thallium is 0.45. The Speed of Sound of Tl is 818 m/s.
Hardness	26.4 MPa 1.2 MPa
Bulk Modulus	43 GPa
Shear Modulus	2.8 GPa
Young's Modulus	8 GPa
Poisson Ratio	0.45
Speed of Sound	818 m/s
Classification
The CAS Group of Thallium is IIIB. The IUPAC Group of Tl is IIIA. The Glawe Number of Element 81 is 81. The Mendeleev Number of Thallium (Tl) is 85. The Pettifor Number of Thallium is 78. The Goldschmidt Class of Tl is chalcophile.
Category	Post-transition metals, Poor metals
CAS Group	IIIB
IUPAC Group	IIIA
Glawe Number	81
Mendeleev Number	85
Pettifor Number	78
Geochemical Class
Goldschmidt Class	chalcophile
Other
The Dipole Polarizability of Thallium is 50 plus or minus 2 a₀. Tl has a C6 Dispersion Coefficient (GB) of 509 a₀. The Allotropes of Element 81 is . The Neutron Cross Section of Thallium (Tl) is 3.4. The Neutron Mass Absorption of Thallium is 0.00059. The Quantum Numbers of Tl is 2P1/2. The Space Group of Element 81 is 194 (P63/mmc).
Gas Basicity
Dipole Polarizability	50 ± 2 a₀
C6 Dispersion Coefficient	509 a₀
Allotropes
Neutron Cross Section	3.4
Neutron Mass Absorption	0.00059
Quantum Numbers	2P1/2
Space Group	194 (P63/mmc)

Isotopes of Thallium

Stable Isotopes	2
Unstable Isotopes	41
Radioactive Isotopes	41

¹⁷⁶Tl

Mass Number	176
Neutron Number	95
Relative Atomic Mass	176.000627731 ± 0.000089166 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	6.2 ± 2.3 ms
Spin	3
Quadrupole Moment
Discovery Year	2004
Parity	-

Decay Mode	Intensity
p (proton emission)	100%
α (α emission)
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)

¹⁷⁷Tl

Mass Number	177
Neutron Number	96
Relative Atomic Mass	176.996414252 ± 0.000023218 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	18 ± 5 ms
Spin	1/2
Quadrupole Moment	0
Discovery Year	1999
Parity	+

Decay Mode	Intensity
α (α emission)	73%
p (proton emission)

¹⁷⁸Tl

Mass Number	178
Neutron Number	97
Relative Atomic Mass	177.995047 ± 0.00011 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	255 ± 9 ms
Spin	4
Quadrupole Moment
Discovery Year	1997
Parity	-

Decay Mode	Intensity
α (α emission)	62%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	38%
β⁺ SF (β⁺-delayed fission)	0.15%

¹⁷⁹Tl

Mass Number	179
Neutron Number	98
Relative Atomic Mass	178.991122185 ± 0.000041495 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	437 ± 9 ms
Spin	1/2
Quadrupole Moment	0
Discovery Year	1983
Parity	+

Decay Mode	Intensity
α (α emission)	60%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)

¹⁸⁰Tl

Mass Number	180
Neutron Number	99
Relative Atomic Mass	179.98991895 ± 0.000075058 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	1.09 ± 0.01 s
Spin	4
Quadrupole Moment
Discovery Year	1987
Parity	-

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	93%
α (α emission)	7%
β⁺ SF (β⁺-delayed fission)	0.0032%

¹⁸¹Tl

Mass Number	181
Neutron Number	100
Relative Atomic Mass	180.986259978 ± 0.000009771 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	2.9 ± 0.1 s
Spin	1/2
Quadrupole Moment	0
Discovery Year	1996
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)
α (α emission)	8.6%

¹⁸²Tl

Mass Number	182
Neutron Number	101
Relative Atomic Mass	181.985692649 ± 0.000012856 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	1.9 ± 0.1 s
Spin	4
Quadrupole Moment
Discovery Year	1991
Parity	-

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)	0.49%
β⁺ SF (β⁺-delayed fission)	3.4%

¹⁸³Tl

Mass Number	183
Neutron Number	102
Relative Atomic Mass	182.982192843 ± 0.000010017 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	6.9 ± 0.7 s
Spin	1/2
Quadrupole Moment	0
Discovery Year	1980
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)
α (α emission)

¹⁸⁴Tl

Mass Number	184
Neutron Number	103
Relative Atomic Mass	183.981874973 ± 0.000010747 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	9.5 ± 0.2 s
Spin	2
Quadrupole Moment
Discovery Year	1976
Parity	-

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	98.78%
α (α emission)	1.22%

¹⁸⁵Tl

Mass Number	185
Neutron Number	104
Relative Atomic Mass	184.978789189 ± 0.000022194 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	19.5 ± 0.5 s
Spin	1/2
Quadrupole Moment	0
Discovery Year	1976
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)

¹⁸⁶Tl

Mass Number	186
Neutron Number	105
Relative Atomic Mass	185.978654787 ± 0.000022276 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	3.5 ± 0.5 s
Spin	2
Quadrupole Moment
Discovery Year	1975
Parity	-

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)
α (α emission)

¹⁸⁷Tl

Mass Number	187
Neutron Number	106
Relative Atomic Mass	186.97590474 ± 0.00000864 Da
G-Factor	3.08 ± 0.12
Abundance
Radioactivity	☢️ Radioactive
Half Life
Spin	1/2
Quadrupole Moment	0
Discovery Year	1976
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)

¹⁸⁸Tl

Mass Number	188
Neutron Number	107
Relative Atomic Mass	187.976020886 ± 0.000032103 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	71 ± 2 s
Spin	2
Quadrupole Moment
Discovery Year	1970
Parity	-

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁸⁹Tl

Mass Number	189
Neutron Number	108
Relative Atomic Mass	188.973573525 ± 0.000008983 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	2.3 ± 0.2 m
Spin	1/2
Quadrupole Moment	0
Discovery Year	1972
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁹⁰Tl

Mass Number	190
Neutron Number	109
Relative Atomic Mass	189.973841771 ± 0.000007784 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	2.6 ± 0.3 m
Spin	2
Quadrupole Moment
Discovery Year	1970
Parity	-

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁹¹Tl

Mass Number	191
Neutron Number	110
Relative Atomic Mass	190.971784093 ± 0.000007889 Da
G-Factor	3.164 ± 0.008
Abundance
Radioactivity	☢️ Radioactive
Half Life
Spin	1/2
Quadrupole Moment	0
Discovery Year	1974
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)

¹⁹²Tl

Mass Number	192
Neutron Number	111
Relative Atomic Mass	191.972225 ± 0.000034 Da
G-Factor	0.0995 ± 0.0015
Abundance
Radioactivity	☢️ Radioactive
Half Life	9.6 ± 0.4 m
Spin	2
Quadrupole Moment
Discovery Year	1961
Parity	-

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁹³Tl

Mass Number	193
Neutron Number	112
Relative Atomic Mass	192.970501994 ± 0.0000072 Da
G-Factor	3.17 ± 0.006
Abundance
Radioactivity	☢️ Radioactive
Half Life	21.6 ± 0.8 m
Spin	1/2
Quadrupole Moment	0
Discovery Year	1960
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁹⁴Tl

Mass Number	194
Neutron Number	113
Relative Atomic Mass	193.971081408 ± 0.000015 Da
G-Factor	0.0695 ± 0.0015
Abundance
Radioactivity	☢️ Radioactive
Half Life	33 ± 0.5 m
Spin	2
Quadrupole Moment	-0.282 ± 0.007
Discovery Year	1960
Parity	-

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)

¹⁹⁵Tl

Mass Number	195
Neutron Number	114
Relative Atomic Mass	194.969774052 ± 0.000011944 Da
G-Factor	3.14 ± 0.08
Abundance
Radioactivity	☢️ Radioactive
Half Life	1.16 ± 0.05 h
Spin	1/2
Quadrupole Moment	0
Discovery Year	1955
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁹⁶Tl

Mass Number	196
Neutron Number	115
Relative Atomic Mass	195.970481189 ± 0.000013 Da
G-Factor	0.036 ± 0.0015
Abundance
Radioactivity	☢️ Radioactive
Half Life	1.84 ± 0.03 h
Spin	2
Quadrupole Moment	-0.178 ± 0.014
Discovery Year	1955
Parity	-

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁹⁷Tl

Mass Number	197
Neutron Number	116
Relative Atomic Mass	196.969560492 ± 0.000014573 Da
G-Factor	3.14 ± 0.04
Abundance
Radioactivity	☢️ Radioactive
Half Life	2.84 ± 0.04 h
Spin	1/2
Quadrupole Moment	0
Discovery Year	1955
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁹⁸Tl

Mass Number	198
Neutron Number	117
Relative Atomic Mass	197.970446669 ± 0.0000081 Da
G-Factor	0 ± 0.005
Abundance
Radioactivity	☢️ Radioactive
Half Life	5.3 ± 0.5 h
Spin	2
Quadrupole Moment
Discovery Year	1949
Parity	-

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

¹⁹⁹Tl

Mass Number	199
Neutron Number	118
Relative Atomic Mass	198.969877 ± 0.00003 Da
G-Factor	3.18 ± 0.04
Abundance
Radioactivity	☢️ Radioactive
Half Life	7.42 ± 0.08 h
Spin	1/2
Quadrupole Moment	0
Discovery Year	1949
Parity	+

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

²⁰⁰Tl

Mass Number	200
Neutron Number	119
Relative Atomic Mass	199.970963608 ± 0.000006182 Da
G-Factor	0.02 ± 0.005
Abundance
Radioactivity	☢️ Radioactive
Half Life	26.1 ± 0.1 h
Spin	2
Quadrupole Moment
Discovery Year	1949
Parity	-

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%

²⁰¹Tl

Mass Number	201
Neutron Number	120
Relative Atomic Mass	200.970820235 ± 0.000015228 Da
G-Factor	3.198 ± 0.006
Abundance
Radioactivity	☢️ Radioactive
Half Life	3.0421 ± 0.0008 d
Spin	1/2
Quadrupole Moment	0
Discovery Year	1950
Parity	+

Decay Mode	Intensity
ϵ (electron capture)	100%

²⁰²Tl

Mass Number	202
Neutron Number	121
Relative Atomic Mass	201.972108874 ± 0.000001972 Da
G-Factor	0.03 ± 0.005
Abundance
Radioactivity	☢️ Radioactive
Half Life	12.31 ± 0.08 d
Spin	2
Quadrupole Moment
Discovery Year	1940
Parity	-

Decay Mode	Intensity
ϵ (electron capture)	100%

²⁰³Tl

Mass Number	203
Neutron Number	122
Relative Atomic Mass	202.972344098 ± 0.000001257 Da
G-Factor
Abundance	29.515 ± 0.044
Radioactivity	Stable
Half Life	Not Radioactive ☢️
Spin	1/2
Quadrupole Moment	0
Discovery Year	1931
Parity	+

²⁰⁴Tl

Mass Number	204
Neutron Number	123
Relative Atomic Mass	203.97386342 ± 0.000001238 Da
G-Factor	0.045 ± 0.005
Abundance
Radioactivity	☢️ Radioactive
Half Life	3.783 ± 0.012 y
Spin	2
Quadrupole Moment
Discovery Year	1953
Parity	-

Decay Mode	Intensity
β⁻ (β⁻ decay)	97.08%
EC+B+	2.92%

²⁰⁵Tl

Mass Number	205
Neutron Number	124
Relative Atomic Mass	204.974427318 ± 0.00000133 Da
G-Factor
Abundance	70.485 ± 0.044
Radioactivity	Stable
Half Life	Not Radioactive ☢️
Spin	1/2
Quadrupole Moment	0
Discovery Year	1931
Parity	+

²⁰⁶Tl

Mass Number	206
Neutron Number	125
Relative Atomic Mass	205.976110108 ± 0.00000138 Da
G-Factor	0
Abundance
Radioactivity	☢️ Radioactive
Half Life	4.202 ± 0.011 m
Spin	0
Quadrupole Moment	0
Discovery Year	1935
Parity	-

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²⁰⁷Tl

Mass Number	207
Neutron Number	126
Relative Atomic Mass	206.977418605 ± 0.000005839 Da
G-Factor	3.738 ± 0.01
Abundance
Radioactivity	☢️ Radioactive
Half Life	4.77 ± 0.02 m
Spin	1/2
Quadrupole Moment	0
Discovery Year	1908
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²⁰⁸Tl

Mass Number	208
Neutron Number	127
Relative Atomic Mass	207.982018006 ± 0.000001989 Da
G-Factor	0.0582 ± 0.0026
Abundance
Radioactivity	☢️ Radioactive
Half Life	3.053 ± 0.004 m
Spin	5
Quadrupole Moment
Discovery Year	1909
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²⁰⁹Tl

Mass Number	209
Neutron Number	128
Relative Atomic Mass	208.985351713 ± 0.000006559 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	2.162 ± 0.007 m
Spin	1/2
Quadrupole Moment	0
Discovery Year	1950
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)

²¹⁰Tl

Mass Number	210
Neutron Number	129
Relative Atomic Mass	209.990072942 ± 0.000012456 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	1.3 ± 0.03 m
Spin	5
Quadrupole Moment
Discovery Year	1909
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	0.009%

²¹¹Tl

Mass Number	211
Neutron Number	130
Relative Atomic Mass	210.993475 ± 0.000045 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	81 ± 16 s
Spin	1/2
Quadrupole Moment	0
Discovery Year	1998
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	2.2%

²¹²Tl

Mass Number	212
Neutron Number	131
Relative Atomic Mass	211.998335 ± 0.000215 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	31 ± 8 s
Spin	5
Quadrupole Moment
Discovery Year	1998
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	1.8%

²¹³Tl

Mass Number	213
Neutron Number	132
Relative Atomic Mass	213.001915 ± 0.000029 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	23.8 ± 4.4 s
Spin	1/2
Quadrupole Moment	0
Discovery Year	2010
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	7.6%

²¹⁴Tl

Mass Number	214
Neutron Number	133
Relative Atomic Mass	214.00694 ± 0.00021 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	11 ± 2.4 s
Spin	5
Quadrupole Moment
Discovery Year	2010
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	34%

²¹⁵Tl

Mass Number	215
Neutron Number	134
Relative Atomic Mass	215.010768 ± 0.000322 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	9.7 ± 3.8 s
Spin	1/2
Quadrupole Moment	0
Discovery Year	2010
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	4.6%

²¹⁶Tl

Mass Number	216
Neutron Number	135
Relative Atomic Mass	216.015964 ± 0.000322 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life	5.9 ± 3.3 s
Spin	5
Quadrupole Moment
Discovery Year	2010
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	11.5%

²¹⁷Tl

Mass Number	217
Neutron Number	136
Relative Atomic Mass	217.020032 ± 0.000429 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life
Spin	1/2
Quadrupole Moment	0
Discovery Year	2010
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)
β⁻ n (β⁻-delayed neutron emission)

²¹⁸Tl

Mass Number	218
Neutron Number	137
Relative Atomic Mass	218.025454 ± 0.000429 Da
G-Factor
Abundance
Radioactivity	☢️ Radioactive
Half Life
Spin	6
Quadrupole Moment
Discovery Year
Parity	+

Decay Mode	Intensity
β⁻ (β⁻ decay)
β⁻ n (β⁻-delayed neutron emission)

History

Thallium was discovered spectroscopically by Sir William Crookes in 1861, in London. In 1862, Claude-Auguste Lamy used a spectrometer to determine the composition of a selenium-containing substance which was deposited during the production of sulfuric acid from pyrite. He noticed the new green line in the spectra and concluded that a new element was present. From Greek thallos, meanin a green shoot or twig

Discoverers	Sir William Crookes
Discovery Location	England
Discovery Year	1861
Etymology (Name Origin)	Greek: thallos (green twig), for a bright green line in its spectrum.
Pronunciation	THAL-i-em (English)

Thallium and its compounds are highly toxic

Agatha Christie made use of thallium's toxicity in her novel The Pale Horse

Uses

Thallium selenide has been used in a bolometer for infrared detection. Thallium is also used in gamma radiation detection equipment. Thallium oxide has been used to produce glasses with a high index of refraction, and is used in the manufacture of photo cells. Some of the electrodes in dissolved oxygen analyzers contain thallium. 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.

Abundance
Abundance in Earth's crust	0.85 mg/kg
Natural Abundance (Oceans)	0.000019 mg/L
Natural Abundance (Human Body)
Natural Abundance (Meteor)	0.0000078 %
Natural Abundance (Sun)	0.0000001 %
Abundance in Universe	0.00000005 %

Nuclear Screening Constants

1	s	1.5591
2	p	4.5138
2	s	21.3158
3	d	13.4658
3	p	22.6335
3	s	23.5809
4	d	37.6112
4	f	38.1324
4	p	35.7832
4	s	34.9212
5	d	58.975
5	p	53.9115
5	s	51.878
6	p	68.7462
6	s	68.1804

Also Known As

Tl
element 81
81Tl

Translations

Polishtal
Frenchthallium
Italiantallio
Norwegian Bokmålthallium
Spanishtalio
Esperantotaliumo
Norwegian Nynorskthallium
Hungariantallium
GermanThallium
Czechthallium
Amharicታሊየም
AragoneseTalio
Arabicثاليوم
AzerbaijaniTallium
BelarusianТалій
Bulgarianталий
Banglaথ্যালিয়াম
BretonTaliom
Bosniantalij
Catalantal·li
CorsicanTalliu
ChuvashТалли
WelshThaliwm
Danishthallium
Greekθάλλιο
Estoniantallium
Basquetalio
Persianتالیم
Finnishtallium
FriulianTali
IrishTailliam
Galiciantalio
ManxThallium
Hakka Chinesethallium
Hebrewתליום
Fiji HindiThallium
Croatiantalij
Haitian CreoleTalyòm
Armenianթալիում
InterlinguaThallium
Indonesiantalium
Idotalio
Icelandicþallín
Japaneseタリウム
Lojbanjinmrtali
Georgianთალიუმი
KazakhТаллий
Kannadaಥಾಲಿಯಮ್
Korean탈륨
KurdishTalyûm
KomiТаллий
Latinthallium
LuxembourgishThallium
LigurianTallio
Lithuaniantalis
Latviantallijs
Macedonianталиум
Malayalamതാലിയം
Marathiथालियम
Western MariТаллий
MalayTalium
Dutchthallium
OccitanTalli
pnbتھیلیم
Portuguesetálio
QuechuaThalyu
Romaniantaliu
Russianталлий
Siciliantalliu
Serbo-CroatianTalijum
Slovaktálium
Sloveniantalij
Serbianталијум
Saterland FrisianThallium
Swedishtallium
SwahiliTali
Tamilதாலியம்
Thaiแทลเลียม
Turkishtalyum
Ukrainianталій
Urduتھیلیئم
VepsTallii
Vietnamesetali
WarayTalyo
KalmykТаллиум
Yiddishטאליום
YorubaThallium
Chinese铊
UzbekTalliy
CebuanoTalyo
Central Kurdishتالیۆم
Odiaଥାଲିଅମ
Gujaratiથેલીયમ
Punjabiਥੈਲੀਅਮ
PiedmonteseTalio
TatarТаллий
Scotsthallium
Northern FrisianThallium
Hindiथैलियम
Cantonese鉈
Belarusian (Taraskievica orthography)таль
Literary Chinese鉈
AlbanianTaliumi
Chinese (China)铊
Chinese (Simplified)铊
Chinese (Traditional)鉈
Chinese (Hong Kong SAR China)鉈
Chinese (Taiwan)鉈
AromanianTaliu
cdothallium
LimburgishThallium
Nepaliथ्यालियम
Burmeseသယ်လီယမ်
Maltesetallju
LombardTàlio
Scottish GaelicTailium
Newariथ्यालियम
Sanskritथ्यालियम
KyrgyzТаллий
Paliथ्यालियम
Teluguథాలియం
Min Nan ChineseThallium
AsturianTaliu
AfrikaansTallium
Bhojpuriथैलियम
Tibetanབེལ་ལིམ
Portuguese (Brazil)tálio
Bashkirталлий
Lingua Franca Novatalio
Low GermanThallium
TagalogTalyo
kbpTaalɩyɔm
Mongolianталли
Wu Chinese铊
oloTallii
TajikТаллий
Uyghurتاللىي
SardinianTàlliu
Moroccan Arabicطاليوم
Egyptian Arabicثاليوم
Pashtoتاليوم
CornishThaliom
BalineseThallium
bclTalyo

Thallium on ChemicalAid

Australian Educational Vocabulary ID	scot/3584
BNCF Thesaurus ID	43733
Biblioteca Nacional de España ID	XX540885
Bibliothèque nationale de France ID	11956478c
Brockhaus Enzyklopädie online ID	thallium
CAB ID	213168
CAS Registry Number	7440-28-0
CPV Supplementary	AA31
ChEBI ID	30440
ChemSpider ID	4514293
Common Procurement Vocabulary	14764000
DSSTOX compound identifier	DTXCID301012091
DSSTox substance ID	DTXSID2036035
Den Store Danske ID	thallium
ECHA Substance Infocard ID	100.028.307
Encyclopædia Britannica Online ID	science/thallium
Encyclopædia Universalis ID	thallium
Freebase ID	/m/025skld
GND ID	4059684-9
Great Russian Encyclopedia Online ID	4180461
HCIS ID	4477
HSDB ID	4496
ICSC ID	0077
InChI	InChI=1S/Tl
InChIKey	BKVIYDNLLOSFOA-UHFFFAOYSA-N
KBpedia ID	Thallium
Krugosvet article	nauka_i_tehnika/himiya/TALLI.html
Library of Congress authority ID	sh85134473
MeSH descriptor ID	D013793
NALT ID	44819
NDL Authority ID	00572717
NKCR AUT ID	ph116450
Namuwiki ID	탈륨
National Library of Israel J9U ID	987007531870205171
National Library of Latvia ID	000310560
OmegaWiki Defined Meaning	3761
OpenAlex ID	C559099789
PSH ID	5795
PubChem CID	5359464
Store medisinske leksikon ID	thallium
Store norske leksikon ID	thallium
Treccani ID	tallio
UNII	AD84R52XLF
USGS Thesaurus ID	1592
WordNet 3.1 Synset ID	14681997-n
ZVG number	7810

Thallium (Tl)

Properties

Isotopes of Thallium

176Tl

177Tl

178Tl

179Tl

180Tl

181Tl

182Tl

183Tl

184Tl

185Tl

186Tl

187Tl

188Tl

189Tl

190Tl

191Tl

192Tl

193Tl

194Tl

195Tl

196Tl

197Tl

198Tl

199Tl

200Tl

201Tl

202Tl

203Tl

204Tl

205Tl

206Tl

207Tl

208Tl

209Tl

210Tl

211Tl

212Tl

213Tl

214Tl

215Tl

216Tl

217Tl

218Tl