Polonium Po (Element 84) of Periodic Table

84 Po (Polonium)

Appearance:  Silvery

Allotropes:  α-Po, β-Po

Mass number:  209

Atomic weight:  208.9824 g/mol

Atomic number (Z):  84

Electrons:  84

Protons:  84

Neutrons:  126

Group:  16

Period:  6

Block:  P

Element category:  Metalloids (semi-metal)

Electrons per shell:  K2, L8, M18, N32, O8, P6

Electron configuration:  1s22s22p63s23p63d104s24p64d105s25p64f145d106s26p4

Phase:  Solid

Melting point:  527 K (254 oC)

Boiling point:  1235 K (962 oC)

Density:  α: 9.196 g/cm3, β: 9.398 g/cm3

Molar volume:  0.00002273 m3/mol

Half life(s):  322×107

Lifetime(s):  464×107

Decay mode:  α decay

Neutron cross section (Barns):  0.5

Heat of fusion:  ca. 13 kJ/mol

Heat of vaporization:  102.91 kJ/mol

Molar heat capacity:  26.4 J/(mol∙K)

Oxidation states:  6, 5, 4, 2, -2

Ion charge:  Po2+, Po4+

Electronegativity:  Pauling scale: 2.0

Valence:  6

Electron affinity:  183.3 kJ/mol

Ionization energies:  1st: 812.1 kJ/mol

Atomic radius:  empirical: 168 pm

Covalent radius:  140±4 pm

Vander waals radius:  197 pm

Crystal structure:  Cubic (α-Po), Rhombohedral (β-Po)

Grid parameters:  3.35 Å

Electrical conductivity:  2300000 S/m

Electrical type:  Conductor

Resistivity:  4.3×10-7 Ω-m

Thermal expansion:  23.5 μm/(m∙K)

Thermal conductivity:  20 W/(m∙K)

Magnetic ordering:  nonmagnetic

CAS Number:  7440-08-6

Naming:  After Polonia (Homeland of Marie Curie)

Discovery:  Pierre and Marie Curie (1898)

First isolation:  Willy Marckwald (1902)

Isotopes:  208Po 209Po 210Po

Polonium Uses:  

It is an Alpha-emitter, used in antistatic device, It is used as source of heat (single gram of polonium will reach a 500 oC as a result of α radiation emitted)

It can be mixed or alloyed with beryllium to provide a source of neutrons.

Biological role of Polonium: 

It is highly toxic due to its radioactivity.

Natural abundance of Polonium: 

It is found in Uranium ores. It is obtained by bombarding bismuth-209 with neutrons to give bismuth-210.


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