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Francium , including Technical Data, Safety Data and its high purity propertiesresearch, applications and other useful facts are discussed below. Scientific facts such as the atomic structure,ionization energyabundance on Earthconductivity and thermal properties are included.

Francium is formerly known as eka-caesium and actinium K. It is the second rarest naturally occurring element, the first being Astatine. Francium has the lowest electronegativities 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 andthorium 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 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 3s2p6d104s2p6d10f14 5s2p6d10 6s2p6 7s1. In its elemental form francium‘s CAS number is 7440-73-5. The francium atom has a radius of and it‘s Van der Waals radius is 

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. 

Abundance. The following table shows the abundance of francium and each of its naturally occurringisotopes on Earth along with the atomic mass for each isotope.
Isotope Atomic Mass % Abundance on Earth
Fr-210 209.99640 -
Fr-211 210.99553 -
Fr-212 211.99618 -

Energy. The ionization energy for francium (the least required energy to release a single electron from the atom in it‘s ground state in the gas phase) is stated in the following table:
1st Ionization Energy 384 kJ mol-1
2nd Ionization Energy kJ mol-1
3rd Ionization Energy kJ mol-1

Conductivity. As to francium‘s electrical and thermal conductivity, the electrical conductivity measured in terms of electrical resistivity @ 20 ?C is - ?Ocm and its electronegativities (or its ability to draw electrons relative to other elements) is 0.7. The thermal conductivity of francium is 0.15 W/cmK. 

Thermal Properties. The melting point and boiling point for francium are stated below. The following chart sets forth the heat of fusion, heat of vaporization and heat of atomization.
Heat of Fusion 2 kJ mol-1
Heat of Vaporization 64 kJ mol-1
Heat of Atomization 73 kJ mol-1

Formula Atomic Number Molecular Weight Electronegativity (Pauling) Density Melting Point Boiling Point Vanderwaals radius Ionic radius Energy of first ionization
Fr 87 [ 223 ] 0.7 1.873 g/cm3 27 °C 677 °C 348pm 194 pm 384 kJ.mol-1