Elements 81-90

Element Information
Atomic Numbers 81 through 90

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This page contains basic information about the elements with atomic numbers 81 through 90. I have tried to make sure the information here is correct. However, if you find a mistake, please e-mail me at apurdy@centurytel.net, and I will correct it as soon as possible.

Thallium Click here to return to periodic table

Symbol	Tl	Name	Thallium
Atomic Number	81	Atomic Mass	204.38 amu
Melting Point	303.5°C	Boiling Point	1457°C
Protons/Electrons	81	Neutrons	123
Classification	Other Metal	State	Solid
Density	11.85 g/cm³	Specific Heat	6 / 13
Electronegativity	^1.83	Atomic Radius	170 pm
# of Isotopes	²	Color	bluish-gray
Energy Levels	⁶	Crystal Structure	hexagonal

Sir William Crookes discovered thallium in 1861. Crookes presumed the element was sulfur-like,but in 1862, he and Claude-Auguste Lamy independently isolated thallium. They found it to be a metal unlike the elements in the group containing sulfur.

Uses - IR detectors, photocells, rat and ant poison

Lead Click here to return to periodic table

Symbol	Pb	Name	Lead
Atomic Number	82	Atomic Mass	207.19 amu
Melting Point	327.5°C	Boiling Point	1744°C
Protons/Electrons	82	Neutrons	125
Classification	Other Metal	State	Solid
Density	11.29 g/cm³	Period/Group	6 / 14
Electronegativity	^2.1	Atomic Radius	146 pm
# of Isotopes	⁴	Color	gray
Energy Levels	⁶	Crystal Structure	cubic

Lead was known in ancient times, and the alchemists of old believed it to be the oldest of all metals.

Uses - batteries, solder, paints, shielding against radiation, sound absorber, used by the Romans for plumbing

Bismuth Click here to return to periodic table

Symbol	Bi	Name	Bismuth
Atomic Number	83	Atomic Mass	208.9806 amu
Melting Point	271.3°C	Boiling Point	1560°C
Protons/Electrons	83	Neutrons	126
Classification	Other Metal	State	Solid
Density	9.747 g/cm³	Period/Group	6 / 15
Electronegativity	^2.02	Atomic Radius	150 pm
# of Isotopes	¹	Color	white
Energy Levels	⁶	Crystal Structure	rhombohedral

Bismuth was described by a German monk, Basil Valentine, in 1450.

Uses - antacid, fusible alloy, pharmaceuticals, fuses, production of malleable irons, catalyst for making acrylic fibers, cosmetics

Polonium Click here to return to periodic table

Symbol	Po	Name	Polonium
Atomic Number	84	Atomic Mass	(209) amu
Melting Point	254°C	Boiling Point	962°C
Protons/Electrons	84	Neutrons	125
Classification	Other Metal	State	Solid
Density	9.4 g/cm³	Specific Heat	6 / 16
Electronegativity	²	Atomic Radius	168 pm
# of Isotopes	¹	Color	blue
Energy Levels	⁶	Crystal Structure	cubic

Polonium was discovered in 1898 by Pierre and Marie Curie.

Uses - thermoelectric power, source of neutrons, elimination of static charges in textile mills

Astatine Click here to return to periodic table

Symbol	At	Name	Astatine
Atomic Number	85	Atomic Mass	(210) amu
Melting Point	302°C	Boiling Point	337°C
Protons/Electrons	85	Neutrons	125
Classification	Metalloid	State	Solid
Density	no data	Period/Group	6 / 17
Electronegativity	2.2	Atomic Radius	127 pm
# of Isotopes	0	Color	no data
Energy Levels	6	Crystal Structure	no data

Astatine was first synthetically produced in 1940 at the University of California by Dale R. Corson, K.R. MacKenzie, and Emilio Segrè, who bombarded bismuth with accelerated alpha particles to yield astatine and neutrons.

Uses - no uses known

Radon Click here to return to periodic table

Symbol	Rn	Name	Radon
Atomic Number	86	Atomic Mass	(222) amu
Melting Point	- 71°C	Boiling Point	- 62°C
Protons/Electrons	86	Neutrons	136
Classification	Noble Gas	State	Gas
Density	0.00973 g/cm³	Period/Group	6 / 18
Electronegativity	^NA	Atomic Radius	120 pm
# of Isotopes	⁰	Color	colorless
Energy Levels	⁶	Crystal Structure	cubic

The longest lived isotope, radon-222, was discovered in 1900 by the German chemist, Friedrich E. Dorn.

Uses - earthquake prediction, treatment of cancer

Francium Click here to return to periodic table

Symbol	Fr	Name	Francium
Atomic Number	87	Atomic Mass	(223) amu
Melting Point	27.2°C	Boiling Point	677°C
Protons/Electrons	87	Neutrons	136
Classification	Alkali Metal	State	Solid
Density	1.87 g/cm³	Period/Group	7 / 1
Electronegativity	^0.7	Atomic Radius	no data
# of Isotopes	¹	Color	no data
Energy Levels	⁷	Crystal Structure	cubic

Francium was discovered by Marguerite Perey in 1939.

Uses - no uses known

Radium Click here to return to periodic table

Symbol	Ra	Name	Radium
Atomic Number	88	Atomic Mass	(226) amu
Melting Point	~700°C	Boiling Point	~ 1737°C
Protons/Electrons	88	Neutrons	138
Classification	Alkaline Earth Metal	State	Solid
Density	~ 5 g/cm³	Period/Group	7 / 2
Electronegativity	^0.9	Atomic Radius	215 pm
# of Isotopes	⁴	Color	white
Energy Levels	7	Crystal Structure	cubic

Radium was discovered in 1898 by Pierre and Marie Curie and an assistant, G. Bémont.

Uses - neutron source, treating cancer, self-luminous paints

Actinium Click here to return to periodic table

Symbol	Ac	Name	Actinium
Atomic Number	89	Atomic Mass	(227) amu
Melting Point	1050°C	Boiling Point	3200°C
Protons/Electrons	89	Neutrons	138
Classification	Transition Metal	State	Solid
Density	10.07 g/cm³	Period/Group	7 / 3
Electronegativity	^1.1	Atomic Radius	195 pm
# of Isotopes	²	Color	silvery-white
Energy Levels	⁷	Crystal Structure	cubic

Actinium was first discovered in 1899 by André-Louis Debierne in pitchblende residues left after the Curies had extracted radium.

Uses - thermoelectric power, source of neutrons

Thorium Click here to return to periodic table

Symbol	Th	Name	Thorium
Atomic Number	90	Atomic Mass	232.038 amu
Melting Point	1842°C	Boiling Point	4820°C
Protons/Electrons	90	Neutrons	142
Classification	Metal	State	Solid
Density	11.724 g/cm³	Group	Actinoid
Electronegativity	^1.3	Atomic Radius	179 pm
# of Isotopes	³	Color	white
Energy Levels	⁷	Crystal Structure	cubic

Thorium was discovered by Jöns Jacob Berzelius in 1828.

Uses - gas mantles, strong alloys, ultraviolet photoelectric cells, laboratory crucibles, source of nuclear energy

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