Francium

223

About Francium

Francium is the second rarest and the most unstable naturally occurring element on the periodic table; only astatine is rarer. A product of a disintegration of actinium, which undergoes beta-disintegration 99% of the time, francium is so highly radioactive that its most stable isotope (Francium-233, formerly known as actinium-K) has a half-life of merely 22 minutes. As such, only 20-30 grams of the element are present at any given time in the earth’s crust, limited to trace amounts in uranium and thorium ores.

Francium can be produced in the laboratory via bombardment of thorium with protons or radium with neutrons, but only in small quantities--the largest amount ever synthesized was a cluster of 30,000 atoms. The element has never been observed in bulk; with the lowest electronegativity of any element on the periodic table, it would immediately vaporize due to the extreme heat of decay. Thus, scientists estimate that francium’s theoretical properties are similar to the other members of the alkali metals family. There are no commercial applications for francium because of its instability.

Dmitri Mendeleev predicted the existence of Francium in the 1870's, calling it “eka-caesium” because of its similarity to cesium (“eka” meaning one element down on the periodic table). The element was discovered by French chemist Marguerite Catherine Perey of the Curie Institute in 1939 while analyzing the decay of actinium; named for her country of origin, Francium would become the last naturally-occurring element to be discovered rather than being synthesized in a laboratory.

Francium Properties

Francium Bohr Model

Francium is a S-Block, Group 1, Period 7 element. The number of electrons in each of Francium's shells is 2,8,18,32,18,8,1 and its electronic configuration is 1s² 2s²p⁶ 3s²p⁶d¹⁰ 4s²p⁶d¹⁰f¹⁴ 5s²p⁶d¹⁰ 6s²p⁶ 7s¹. In its elemental form francium's CAS number is 7440-73-5. The francium atom has a radius of 270.pm and it's Van der Waals radius is 348.pm. Francium was discovered by Marguerite Perey of the Curie Institute in Paris, France in 1939 although its existence was predicted by Mendeleev during the 1870's.

Francium, formerly known as eka-caesium and actinium K, is the second rarest naturally occurring element, the first being Astatine. Francium has the lowest electronegativitiy of all known elements and it was the last element discovered in nature. Outside of the laboratory, only trace amounts of francium can be found in uranium and thorium ores. Out of all of the naturally occurring elements, francium is the most unstable. Due to its rarity and instability, commercial applications for francium do not exist. Francium information, including technical data, properties, research, and other useful facts are discussed below. Scientific facts such as the atomic structure, ionization energy, conductivity and thermal properties are also included.

General Properties

Symbol:	Fr
Atomic Number:	87
Atomic Weight:	223
Element Category:	alkali metal
Group, Period, Block:	1, 7, s
Color:	silver-gray/metallic
Other Names:	N/A

Physical Properties

Melting Point:	21°C, 69.8°F, 294.15 K
Boiling Point:	Unknown
Density:	Unknown
Liquid Density @ Melting Point:	N/A
Density @ 20°C:	1.873 g/cm³
Density of Solid:	2900 (estimated) kg·m³
Specific Heat:	N/A
Superconductivity Temperature:	N/A
Triple Point:	2.177 K, 5.043 kPa
Critical Point:	5.1953 K, 0.22746 MPa
Heat of Fusion (kJ·mol^-1):	about 2
Heat of Vaporization (kJ·mol^-1):	about 65
Heat of Atomization (kJ·mol^-1):	about 64
Thermal Conductivity:	15 W·m¹·K¹
Thermal Expansion:	N/A
Electrical Resistivity:	3 µ (calculated)·m
Tensile Strength:	N/A
Molar Heat Capacity:	N/A
Young's Modulus:	N/A
Shear Modulus:	N/A
Bulk Modulus:	N/A
Poisson Ratio:	N/A
Mohs Hardness:	N/A
Vickers Hardness:	N/A
Brinell Hardness:	N/A
Speed of Sound:	N/A
Pauling Electronegativity:	0.7
Sanderson Electronegativity:	N/A
Allred Rochow Electronegativity:	0.86
Mulliken-Jaffe Electronegativity:	0.68 (s orbital)
Allen Electronegativity:	N/A
Pauling Electropositivity:	3.3
Reflectivity (%):	N/A
Refractive Index:	N/A

Chemical Properties

Electrons:	87
Protons:	87
Neutrons:	136
Electron Configuration:	1s² 2s²p⁶ 3s²p⁶d¹⁰ 4s²p⁶d¹⁰f¹⁴ 5s²p⁶d¹⁰ 6s²p⁶ 7s¹
Atomic Radius:	N/A
Atomic Radius, non-bonded (Å):	3.48
Covalent Radius:	260 pm
Covalent Radius (Å):	2.42
Van der Waals Radius:	348 pm
Oxidation States:	1 (strongly basic oxide)
Phase:	Solid
Crystal Structure:	cubic body-centered
Magnetic Ordering:	paramagnetic
Electron Affinity (kJ·mol^-1)	46.892
1^st Ionization Energy:	380 kJ·mol^-1
2^nd Ionization Energy:	N/A
3^rd Ionization Energy:	N/A

Identifiers

CAS Number:	7440-73-5
EC Number:	N/A
MDL Number:	N/A
Beilstein Number:	N/A
SMILES Identifier:	[Fr]
InChI Identifier:	InChI=1S/Fr
InChI Key:	KLMCZVJOEAUDNE-UHFFFAOYSA-N
PubChem CID:	6328145
ChemSpider ID:	4886484

Abundance

Earth - Total:	N/A
Mercury - Total:	N/A
Venus - Total:	N/A
Earth - Seawater (Oceans), ppb by weight:	N/A
Earth - Seawater (Oceans), ppb by atoms:	N/A
Earth - Crust (Crustal Rocks), ppb by weight:	N/A
Earth - Crust (Crustal Rocks), ppb by atoms:	N/A
Sun - Total, ppb by weight:	N/A
Sun - Total, ppb by atoms:	N/A
Stream, ppb by weight:	N/A
Stream, ppb by atoms:	N/A
Meterorite (Carbonaceous), ppb by weight:	N/A
Meterorite (Carbonaceous), ppb by atoms:	N/A
Typical Human Body, ppb by weight:	N/A
Typical Human Body, ppb by atom:	N/A
Universe, ppb by weight:	N/A
Universe, ppb by atom:	N/A

History

Discovered By:	Marguerite Perey
Discovery Date:	1939
First Isolation:	Marguerite Perey (1939)

Francium Isotopes

Francium has no stable isotopes.

Nuclide	Isotopic Mass	Half-Life	Mode of Decay	Nuclear Spin	Magnetic Moment	Binding Energy (MeV)	Natural Abundance (% by atom)
¹⁹⁹Fr	199.00726(4)	16(7) ms	Unknown	1/2+#	N/A	1510.04	-
²⁰⁰Fr	200.00657(8)	24(10) ms	a to ¹⁹⁶At	3+#	N/A	1518.12	-
²⁰¹Fr	201.00386(8)	67(3) ms	a to ¹⁹⁶At; ß⁺ to ²⁰¹Rn	(9/2-)	N/A	1526.2	-
²⁰²Fr	202.00337(5)	290(30) ms	a to ¹⁹⁷At; ß⁺ to ²⁰²Rn	(3+)	N/A	1534.28	-
²⁰³Fr	203.000925(17)	0.55(2) s	a to ¹⁹⁸At; ß⁺ to ²⁰³Rn	(9/2-)#	N/A	1542.36	-
²⁰⁴Fr	204.000653(26)	1.7(3) s	a to ¹⁹⁹At; ß⁺ to ²⁰⁴Rn	(3+)	N/A	1550.44	-
²⁰⁵Fr	204.998594(8)	3.80(3) s	a to ²⁰⁰At; ß⁺ to ²⁰⁵Rn	(9/2-)	N/A	1567.83	-
²⁰⁶Fr	205.99867(3)	~16 s	ß⁺ to ²⁰⁶Rn; a to ²⁰¹At	(2+,3+)	N/A	1575.91	-
²⁰⁷Fr	206.99695(5)	14.8(1) s	a to ²⁰²At; ß⁺ to ²⁰⁷Rn	9/2-	N/A	1583.99	-
²⁰⁸Fr	207.99714(5)	59.1(3) s	a to ²⁰³At; ß⁺ to ²⁰⁸Rn	7+	N/A	1592.07	-
²⁰⁹Fr	208.995954(16)	50.0(3) s	a to ²⁰⁴At; ß⁺ to ²⁰⁹Rn	9/2-	N/A	1600.15	-
²¹⁰Fr	209.996408(24)	3.18(6) min	a to ²⁰⁶At; EC to ²¹⁰Rn	6+	4.4	1608.23	-
²¹¹Fr	210.995537(23)	3.10(2) min	a to ²⁰⁷At; EC to ²¹¹Rn	9/2-	4	1616.3	-
²¹²Fr	211.996202(28)	20.0(6) min	a to ²⁰⁸At; EC to ²¹²Rn	5+	4.6	1624.38	-
²¹³Fr	212.996189(8)	34.6(3) s	a to ²⁰⁹At; EC to ²¹³Rn	9/2-	4	1632.46	-
²¹⁴Fr	213.998971(9)	5.0(2) ms	a to ²¹⁰At	(1-)	N/A	1640.54	-
²¹⁵Fr	215.000341(8)	86(5) ns	a to ²¹¹At	9/2-	N/A	1639.3	-
²¹⁶Fr	216.003198(15)	0.70(2) µs	a to ²¹²At; EC to ²¹⁶Rn	(1-)	N/A	1647.38	-
²¹⁷Fr	217.004632(7)	16.8(19) µs	a to ²¹³At	9/2-	N/A	1655.46	-
²¹⁸Fr	218.007578(5)	1.0(6) ms	a to ²¹⁴At	1-	N/A	1663.54	-
²¹⁹Fr	219.009252(8)	20(2) ms	a to ²¹⁵At	9/2-	N/A	1671.62	-
²²⁰Fr	220.012327(4)	27.4(3) s	a to ²¹⁶At; ß^- to ²²⁰Ra	1+	N/A	1670.38	-
²²¹Fr	221.014255(5)	4.9(2) min	a to ²¹⁷At; ß^- to ²²¹Ra; ¹⁴C	5/2-	1.58	1678.46	-
²²²Fr	222.017552(23)	14.2(3) min	ß^- to ²²²Ra	2-	0.63	1686.54	-
²²³Fr	223.0197359(26)	22.00(7) min	a to ²¹⁹At	3/2(-)	1.17	1694.62	-
²²⁴Fr	224.02325(5)	3.33(10) min	ß^- to ²²⁴Ra;	1-	0.4	1693.38	-
²²⁵Fr	225.02557(3)	4.0(2) min	ß^- to ²²⁵Ra	3/2-	1.07	1701.46	-
²²⁶Fr	226.02939(11)	49(1) s	ß^- to ²²⁶Ra	1-	0.071	1709.54	-
²²⁷Fr	227.03184(11)	2.47(3) min	ß^- to ²²⁷Ra	1/2+	1.5	1708.3	-
²²⁸Fr	228.03573(22)#	38(1) s	ß^- to ²²⁸Ra	2-	N/A	1716.38	-
²²⁹Fr	229.03845(4)	50.2(4) s	ß^- to ²²⁹Ra	(1/2+)#	N/A	1724.46	-
²³⁰Fr	230.04251(48)#	19.1(5) s	ß^- to ²³⁰Ra	N/A	N/A	1723.22	-
²³¹Fr	231.04544(50)#	17.6(6) s	ß^- to ²³¹Ra	(1/2+)#	N/A	1731.3	-
²³²Fr	232.04977(69)#	5(1) s	ß^- to ²³²Ra	N/A	N/A	1739.38	-