Mendeleev's Periodic Table > Tl - Thallium

Tl - Thallium

The toxic heavy metal thallium was discovered in 1861 by Crookes in London. When freshly exposed to air, thallium exhibits a metallic lustre, but soon develops a bluish-grey tinge, resembling lead in appearance. A heavy oxide builds up on thallium if left in air, and in the presence of water the hydroxide is formed. The metal is very soft and malleable. It can be cut with a knife. The element and its compounds are toxic and should be handled carefully. Thallium may cause cancer.

Atomic number - 81 Density g/mL 11 .85
Atomic weight u 204 .37 Melting point K 577
Bonding radius A 1 .48 Boiling point K 1746
Atomic radius A 2 .08 Heat of vaporization kJ/mol 164 .1
Ionization Potential V 6 .108 Heat of fusion kJ/mol 4 .142
Electronegativity - 2 .04 Specific heat J/gK 0 .13
The oxide is mildly basic. Crystal are hexagonal.
Electron config. : [Xe] 4f14 5d10 6s2 6p1

Isotopes of Tl (Thallium):

MASS abundancy
Halflife
Particle, Energy
Decay Product(s)
Isotopic Mass		 179
0.16 sec
a,6.860 MeV
Au-175
178.99165 		179a
1.4 msec
a,6.860 MeV
Au-175
178.99165 		180
1.9 sec
a/EC/ECF,6.258
Au-176/Hg-180/?
179.99023 		181
3.4 sec
EC,8.500 MeV
Hg-181
180.98690
MASS abundancy
Halflife
Particle, Energy
Decay Product(s)
Isotopic Mass		 182
3.1 sec
a/EC,10.100
Au-178/Hg-182
181.98561 		183
6.9 sec
EC,7.600 MeV
Hg-183
182.98260 		183a
60 msec
a,6.850 MeV
Au-179
182.98314 		184
11 sec
a/EC,9.200
Au-180/Hg-184
183.98174
MASS abundancy
Halflife
Particle, Energy
Decay Product(s)
Isotopic Mass		 185
19.5 sec
a/EC,6.600
Au-181/Hg-185
184.97906 		186
27.5 sec
a/EC,8.500
Au-182/Hg-186
185.97852 		187
51 sec
a/EC,5.900
Au-183/Hg-187
186.97616 		188
71 sec
EC,7.800 MeV
Hg-188
187.97592
MASS abundancy
Halflife
Particle, Energy
Decay Product(s)
Isotopic Mass		 189
2.3 min
EC,5.180 MeV
Hg-189
188.97369 		190
2.6 min
EC,7.000 MeV
Hg-190
189.97380 		191

EC,4.490 MeV
Hg-191
190.97188 		192
9.6 min
EC,6.120 MeV
Hg-192
191.97214
MASS abundancy
Halflife
Particle, Energy
Decay Product(s)
Isotopic Mass		 193
21.6 min
EC,3.640 MeV
Hg-193
192.97055 		194
33.0 min
a/EC,5.280
Au-190/Hg-194
193.97105 		195
1.16 hr
EC,2.810 MeV
Hg-195
194.96965 		196
1.84 hr
EC,4.380 MeV
Hg-196
195.97050
MASS abundancy
Halflife
Particle, Energy
Decay Product(s)
Isotopic Mass		 197
2.84 hr
EC,2.180 MeV
Hg-197
196.96953 		198
5.3 hr
EC,3.460 MeV
Hg-198
197.97046 		199
7.42 hr
EC,1.440 MeV
Hg-199
198.96981 		200
26.1 hr
EC,2.456 MeV
Hg-200
199.97094
MASS abundancy
Halflife
Particle, Energy
Decay Product(s)
Isotopic Mass		 201
72.912 hr
EC,1.275 MeV
Hg-201
200.97080 		202
12.23 da
EC,1.364 MeV
Hg-202
201.97209 		203 29.524%

Stable

202.97232 		204
3.78 yr
B-/EC,3.800
Pb-204/Hg-204
203.97384
MASS abundancy
Halflife
Particle, Energy
Decay Product(s)
Isotopic Mass		 205 70.476%

Stable

204.97441 		206
4.199 min
B-,1.533 MeV
Pb-206
205.97609 		207
4.77 min
B-,1.423 MeV
Pb-207
206.97740 		208
3.053 min
B-,5.001 MeV
Pb-208
207.98200
MASS abundancy
Halflife
Particle, Energy
Decay Product(s)
Isotopic Mass		 209
2.20 min
B-,3.980 MeV
Pb-209
208.98534 		210
1.30 min
B-/B-n,5.484
Pb-210/Pb-209
209.99006